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fix: max length of arrays and coding style (#1614)
* Fixed array max length and coding style Max length of arrays was previously an absurdly high integer, instead implemented a numerical upper bound using log2 (max depth of seg tree being logn). Removed `using namespace std;` and `typedef long long ll;` and other competitive coding practices. Added input prompts. * Fixed remaining clang-tidy warnings * Replaced reference parameters with const & or * * Self-tests and documentation * Improved documentation * Added author names Co-authored-by: David Leal <halfpacho@gmail.com>
This commit is contained in:
Soham Roy
GitHub
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//#include <bits/stdc++.h>
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/**
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#incldue < iostream >
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* @file
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#define MAX 4000000
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* @brief Implementation of [Segment Tree]
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using namespace std;
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* (https://en.wikipedia.org/wiki/Segment_tree) data structure
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typedef long long ll;
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*
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void ConsTree(ll arr[], ll segtree[], ll low, ll high, ll pos) {
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* @details
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* A segment tree, also known as a statistic tree, is a tree data structure used
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* for storing information about intervals, or segments. Its classical version
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* allows querying which of the stored segments contain a given point, but our
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* modification allows us to perform (query) any binary operation on any range
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* in the array in O(logN) time. Here, we have used addition (+).
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* For range updates, we have used lazy propagation.
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*
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* * Space Complexity : O(NlogN) \n
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* * Build Time Complexity : O(NlogN) \n
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* * Query Time Complexity : O(logN) \n
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*
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* @author [Madhav Gaba](https://github.com/madhavgaba)
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* @author [Soham Roy](https://github.com/sohamroy19)
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*/
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#include <cassert> /// for assert
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#include <cmath> /// for log2
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#include <iostream> /// for IO operations
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#include <vector> /// for std::vector
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/**
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* @brief Constructs the initial segment tree
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*
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* @param arr input to construct the tree out of
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* @param segtree the segment tree
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* @param low inclusive lowest index of arr to begin at
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* @param high inclusive highest index of arr to end at
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* @param pos index of segtree to fill (eg. root node)
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* @returns void
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*/
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void ConsTree(const std::vector<int64_t> &arr, std::vector<int64_t> *segtree,
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uint64_t low, uint64_t high, uint64_t pos) {
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if (low == high) {
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if (low == high) {
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segtree[pos] = arr[low];
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(*segtree)[pos] = arr[low];
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return;
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return;
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}
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}
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ll mid = (low + high) / 2;
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uint64_t mid = (low + high) / 2;
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ConsTree(arr, segtree, low, mid, 2 * pos + 1);
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ConsTree(arr, segtree, low, mid, 2 * pos + 1);
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ConsTree(arr, segtree, mid + 1, high, 2 * pos + 2);
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ConsTree(arr, segtree, mid + 1, high, 2 * pos + 2);
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segtree[pos] = segtree[2 * pos + 1] + segtree[2 * pos + 2];
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(*segtree)[pos] = (*segtree)[2 * pos + 1] + (*segtree)[2 * pos + 2];
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}
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}
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ll query(ll segtree[], ll lazy[], ll qlow, ll qhigh, ll low, ll high, ll pos) {
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if (low > high)
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/**
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* @brief Returns the sum of all elements in a range
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*
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* @param segtree the segment tree
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* @param lazy for lazy propagation
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* @param qlow lower index of the required query
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* @param qhigh higher index of the required query
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* @param low lower index of query for this function call
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* @param high higher index of query for this function call
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* @param pos index of segtree to consider (eg. root node)
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* @return result of the range query for this function call
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*/
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int64_t query(std::vector<int64_t> *segtree, std::vector<int64_t> *lazy,
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uint64_t qlow, uint64_t qhigh, uint64_t low, uint64_t high,
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uint64_t pos) {
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if (low > high || qlow > high || low > qhigh) {
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return 0;
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return 0;
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if (qlow > high || qhigh < low)
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return 0;
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if (lazy[pos] != 0) {
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segtree[pos] += lazy[pos] * (high - low + 1);
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if (low != high) {
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lazy[2 * pos + 1] += lazy[pos];
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lazy[2 * pos + 2] += lazy[pos];
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}
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lazy[pos] = 0;
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}
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}
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if (qlow <= low && qhigh >= high)
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return segtree[pos];
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if ((*lazy)[pos] != 0) {
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ll mid = (low + high) / 2;
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(*segtree)[pos] += (*lazy)[pos] * (high - low + 1);
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if (low != high) {
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(*lazy)[2 * pos + 1] += (*lazy)[pos];
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(*lazy)[2 * pos + 2] += (*lazy)[pos];
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}
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(*lazy)[pos] = 0;
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}
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if (qlow <= low && qhigh >= high) {
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return (*segtree)[pos];
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}
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uint64_t mid = (low + high) / 2;
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return query(segtree, lazy, qlow, qhigh, low, mid, 2 * pos + 1) +
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return query(segtree, lazy, qlow, qhigh, low, mid, 2 * pos + 1) +
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query(segtree, lazy, qlow, qhigh, mid + 1, high, 2 * pos + 2);
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query(segtree, lazy, qlow, qhigh, mid + 1, high, 2 * pos + 2);
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}
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}
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void update(ll segtree[], ll lazy[], ll start, ll end, ll delta, ll low,
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ll high, ll pos) {
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/**
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if (low > high)
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* @brief Updates a range of the segment tree
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*
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* @param segtree the segment tree
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* @param lazy for lazy propagation
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* @param start lower index of the required query
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* @param end higher index of the required query
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* @param delta integer to add to each element of the range
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* @param low lower index of query for this function call
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* @param high higher index of query for this function call
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* @param pos index of segtree to consider (eg. root node)
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* @returns void
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*/
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void update(std::vector<int64_t> *segtree, std::vector<int64_t> *lazy,
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int64_t start, int64_t end, int64_t delta, uint64_t low,
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uint64_t high, uint64_t pos) {
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if (low > high) {
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return;
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return;
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if (lazy[pos] != 0) {
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segtree[pos] += lazy[pos] * (high - low + 1);
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if (low != high) {
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lazy[2 * pos + 1] += lazy[pos];
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lazy[2 * pos + 2] += lazy[pos];
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}
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lazy[pos] = 0;
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}
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}
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if (start > high || end < low)
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if ((*lazy)[pos] != 0) {
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(*segtree)[pos] += (*lazy)[pos] * (high - low + 1);
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if (low != high) {
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(*lazy)[2 * pos + 1] += (*lazy)[pos];
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(*lazy)[2 * pos + 2] += (*lazy)[pos];
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}
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(*lazy)[pos] = 0;
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}
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if (start > high || end < low) {
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return;
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return;
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}
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if (start <= low && end >= high) {
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if (start <= low && end >= high) {
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segtree[pos] += delta * (high - low + 1);
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(*segtree)[pos] += delta * (high - low + 1);
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if (low != high) {
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if (low != high) {
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lazy[2 * pos + 1] += delta;
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(*lazy)[2 * pos + 1] += delta;
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lazy[2 * pos + 2] += delta;
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(*lazy)[2 * pos + 2] += delta;
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}
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}
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return;
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return;
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}
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}
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ll mid = (low + high) / 2;
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uint64_t mid = (low + high) / 2;
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update(segtree, lazy, start, end, delta, low, mid, 2 * pos + 1);
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update(segtree, lazy, start, end, delta, low, mid, 2 * pos + 1);
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update(segtree, lazy, start, end, delta, mid + 1, high, 2 * pos + 2);
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update(segtree, lazy, start, end, delta, mid + 1, high, 2 * pos + 2);
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segtree[pos] = segtree[2 * pos + 1] + segtree[2 * pos + 2];
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(*segtree)[pos] = (*segtree)[2 * pos + 1] + (*segtree)[2 * pos + 2];
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}
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}
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/**
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* @brief Self-test implementation
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*
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* @returns void
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*/
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static void test() {
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int64_t max = static_cast<int64_t>(2 * pow(2, ceil(log2(7))) - 1);
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assert(max == 15);
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std::vector<int64_t> arr{1, 2, 3, 4, 5, 6, 7}, lazy(max), segtree(max);
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ConsTree(arr, &segtree, 0, 7 - 1, 0);
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assert(query(&segtree, &lazy, 1, 5, 0, 7 - 1, 0) == 2 + 3 + 4 + 5 + 6);
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update(&segtree, &lazy, 2, 4, 1, 0, 7 - 1, 0);
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assert(query(&segtree, &lazy, 1, 5, 0, 7 - 1, 0) == 2 + 4 + 5 + 6 + 6);
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update(&segtree, &lazy, 0, 6, -2, 0, 7 - 1, 0);
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assert(query(&segtree, &lazy, 0, 4, 0, 7 - 1, 0) == -1 + 0 + 2 + 3 + 4);
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}
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/**
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* @brief Main function
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*
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* @return 0 on exit
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*/
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int main() {
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int main() {
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ll n, c;
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test(); // run self-test implementations
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scanf("%lld %lld", &n, &c);
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ll arr[n] = {0}, p, q, v, choice;
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std::cout << "Enter number of elements: ";
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ll segtree[MAX], lazy[MAX] = {0};
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ConsTree(arr, segtree, 0, n - 1, 0);
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uint64_t n = 0;
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while (c--) {
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std::cin >> n;
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scanf("%lld", &choice);
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if (choice == 0) {
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uint64_t max = static_cast<uint64_t>(2 * pow(2, ceil(log2(n))) - 1);
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scanf("%lld %lld %lld", &p, &q, &v);
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std::vector<int64_t> arr(n), lazy(max), segtree(max);
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update(segtree, lazy, p - 1, q - 1, v, 0, n - 1, 0);
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} else {
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int choice = 0;
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scanf("%lld %lld", &p, &q);
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std::cout << "\nDo you wish to enter each number?:\n"
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printf("%lld\n", query(segtree, lazy, p - 1, q - 1, 0, n - 1, 0));
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"1: Yes\n"
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"0: No (default initialize them to 0)\n";
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std::cin >> choice;
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if (choice == 1) {
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std::cout << "Enter " << n << " numbers:\n";
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for (int i = 1; i <= n; i++) {
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std::cout << i << ": ";
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std::cin >> arr[i];
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}
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}
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}
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}
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ConsTree(arr, &segtree, 0, n - 1, 0);
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do {
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std::cout << "\nMake your choice:\n"
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"1: Range update (input)\n"
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"2: Range query (output)\n"
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"0: Exit\n";
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std::cin >> choice;
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if (choice == 1) {
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std::cout << "Enter 1-indexed lower bound, upper bound & value:\n";
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uint64_t p = 1, q = 1, v = 0;
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std::cin >> p >> q >> v;
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update(&segtree, &lazy, p - 1, q - 1, v, 0, n - 1, 0);
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} else if (choice == 2) {
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std::cout << "Enter 1-indexed lower bound & upper bound:\n";
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uint64_t p = 1, q = 1;
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std::cin >> p >> q;
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std::cout << query(&segtree, &lazy, p - 1, q - 1, 0, n - 1, 0);
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std::cout << "\n";
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}
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} while (choice > 0);
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return 0;
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return 0;
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}
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}
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