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

http://www.geeksforgeeks.org/largest-subarray-with-equal-number-of-0s-and-1s/

#include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
#include <stack>
#include <string>
#include <fstream>
#include <map>
using namespace std;

void findsubarray(int arr[], int n) {
    map<int, vector<int> > S;
    int sum = 0;
    for (int i = 0; i < n; i++) {
        sum += (arr[i] == 0? -1 : 1);
        if (S.find(sum) != S.end()) S[sum].push_back(i);
        else S[sum] = vector<int>(1, i);
    }
    int ans = 0;
    for (map<int, vector<int> >::iterator it = S.begin(); it != S.end(); it++) {
        if ((it->first) == 0) ans = max(ans, (it->second)[(it->second).size()-1]+1);
        else ans = max(ans, (it->second)[(it->second).size()-1] - (it->second)[0]);
    }
    cout << ans << endl;
}

int main() {
    int arr[7] = {1, 0, 1, 1, 0, 1, 1};
    findsubarray(arr, 7);
    return 0;
}