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Update Longest Increasing Subsequence (nlogn).cpp

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John Law 2019-10-08 23:58:49 +08:00 committed by GitHub
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1 changed files with 36 additions and 29 deletions
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Dynamic Programming/Longest Increasing Subsequence (nlogn).cpp
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@ -3,37 +3,44 @@
// tested on : https://cses.fi/problemset/task/1145/
#include <bits/stdc++.h>
using namespace std;
int LIS(int arr[], int n)
{
set<int> active; // The current built LIS.
active.insert(arr[0]);
// Loop through every element.
for(int i=1; i<n; ++i){
auto get = active.lower_bound(arr[i]);
if( get == active.end() ){ active.insert(arr[i]); } // current element is the greatest so LIS increases by 1.
else{
int val = *get; // we find the position where arr[i] will be in the LIS. If it is in the LIS already we do nothing
if( val > arr[i] ){
// else we remove the bigger element and add a smaller element (which is arr[i]) and continue;
active.erase(get);
active.insert(arr[i]);
}
}
}
return active.size(); // size of the LIS.
}
int main(int argc, char const *argv[])
{
int n;
cout << "Enter size of array: ";
cin >> n;
int a[n];
cout << "Enter array elements: ";
for (int i = 0; i < n; ++i)
set < int > active; // The current built LIS.
active.insert(arr[0]);
// Loop through every element.
for (int i = 1; i < n; ++i)
{
auto get = active.lower_bound(arr[i]);
if (get == active.end())
{
cin >> a[i];
}
cout << LIS(a, n) << endl;
return 0;
active.insert(arr[i]);
} // current element is the greatest so LIS increases by 1.
else
{
int val = * get; // we find the position where arr[i] will be in the LIS. If it is in the LIS already we do nothing
if (val > arr[i])
{
// else we remove the bigger element and add a smaller element (which is arr[i]) and continue;
active.erase(get);
active.insert(arr[i]);
}
}
}
return active.size(); // size of the LIS.
}
int main(int argc, char const * argv[])
{
int n;
cout << "Enter size of array: ";
cin >> n;
int a[n];
cout << "Enter array elements: ";
for (int i = 0; i < n; ++i)
{
cin >> a[i];
}
cout << LIS(a, n) << endl;
return 0;
}