OpenSoure_Repos/TheAlgorithms-C-Plus-Plus
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Sushil Kumar 2020-08-21 12:08:06 +05:30 committed by GitHub
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1 changed files with 22 additions and 13 deletions
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search/median_search.cpp
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@ -1,14 +1,20 @@
/** // Given an array A[1,...,n] of n numbers and an index idx, idx, where 1≤idx≤ n, 1≤idx≤ n, find the i-th smallest element of A.
* \file
* \brief [Median search](https://en.wikipedia.org/wiki/Median_search) algorithm
* cases from [here](https://brilliant.org/wiki/median-finding-algorithm/)
* \ingroup median search
*/
#include <iostream> #include <iostream>
#include <algorithm> #include <algorithm>
#include <vector> #include <vector>
/**
* @namespace search
* @brief Search algorithms
*/
namespace search {
/**
* @namespace median_search
* @brief Functions for [Median search](https://en.wikipedia.org/wiki/Median_search) algorithm
* @cases from [here](https://brilliant.org/wiki/median-finding-algorithm/)
*/
namespace median_search {
/* Assume that all the elements of A are distinct /* Assume that all the elements of A are distinct
def median_of_medians(A, i): def median_of_medians(A, i):
@ -43,8 +49,8 @@
* print median_of_medians(B,4) #should be 5 * print median_of_medians(B,4) #should be 5
*/ */
int median_of_medians(std::vector<int> a, int idx){ int median_of_medians(std::vector<int> a, int idx){ // Search the element in **a** whose index is **idx** and return element at index **idx** in **a** (a[idx])
int pivot = 0; // initialized with zero int pivot = 0; // initialized with zero
std::vector<int> m; std::vector<int> m;
int r = a.size(); int r = a.size();
for(int i = 0; i < r; i += 5){ for(int i = 0; i < r; i += 5){
@ -81,9 +87,12 @@ int median_of_medians(std::vector<int> a, int idx){
return pivot; return pivot;
} }
} }
} // namespace median_search
} // namespace search
/* Main function*/ /**
* Main function
*/
int main() int main()
{ {
int n = 0; int n = 0;
@ -95,9 +104,9 @@ int main()
std::cin >> a[i]; std::cin >> a[i];
} }
std::cout << "Median: "; // Median defination: https://en.wikipedia.org/wiki/Median std::cout << "Median: "; // Median defination: https://en.wikipedia.org/wiki/Median
int x = median_of_medians(a, (n - 1) / 2); int x = search::median_search::median_of_medians(a, (n - 1) / 2);
if(n % 2 == 0){ if(n % 2 == 0){
int y = median_of_medians(a, n / 2); int y = search::median_search::median_of_medians(a, n / 2);
std::cout << (float(x) + float(y))/2.0; std::cout << (float(x) + float(y))/2.0;
} }
else{ else{
@ -108,7 +117,7 @@ int main()
int idx = 0; int idx = 0;
std::cin >> idx; std::cin >> idx;
idx--; idx--;
std::cout << idx + 1<< "-th smallest element: " << median_of_medians(a, idx) << '\n'; std::cout << idx + 1<< "-th smallest element: " << search::median_search::median_of_medians(a, idx) << '\n';
return 0; return 0;
} }