Data Structure Array: Largest subarray with equal number of 0s and 1s

 1 #include <iostream>
 2 #include <vector>
 3 #include <algorithm>
 4 #include <queue>
 5 #include <stack>
 6 #include <string>
 7 #include <fstream>
 8 #include <map>
 9 using namespace std;
10 
11 void findsubarray(int arr[], int n) {
12     map<int, vector<int> > S;
13     int sum = 0;
14     for (int i = 0; i < n; i++) {
15         sum += (arr[i] == 0? -1 : 1);
16         if (S.find(sum) != S.end()) S[sum].push_back(i);
17         else S[sum] = vector<int>(1, i);
18     }
19     int ans = 0;
20     for (map<int, vector<int> >::iterator it = S.begin(); it != S.end(); it++) {
21         if ((it->first) == 0) ans = max(ans, (it->second)[(it->second).size()-1]+1);
22         else ans = max(ans, (it->second)[(it->second).size()-1] - (it->second)[0]);
23     }
24     cout << ans << endl;
25 }
26 
27 int main() {
28     int arr[7] = {1, 0, 1, 1, 0, 1, 1};
29     findsubarray(arr, 7);
30     return 0;
31 }