func_code_string: #include <bits/stdc++.h>   using namespace std;   const int MOD = (int)1e9 + 7;   const int INF = (int)1e9;   const long long LINF = (long long)1e18;   const long double PI = acos((long double)-1);   const long double EPS = 1e-9;   long long gcd(long long a, long long b) {     long long r;     while (b) {       r = a % b;       a = b;       b = r;     }     return a;   }   long long lcm(long long a, long long b) { return a / gcd(a, b) * b; }   long long fpow(long long n, long long k, int p = MOD) {     long long r = 1;     for (; k; k >>= 1) {       if (k & 1) r = r * n % p;       n = n * n % p;     }     return r;   }   void addmod(int& a, int val, int p = MOD) {     if ((a = (a + val)) >= p) a -= p;   }   void submod(int& a, int val, int p = MOD) {     if ((a = (a - val)) < 0) a += p;   }   int mult(int a, int b, int p = MOD) { return (long long)a * b % p; }   int inv(int a, int p = MOD) { return fpow(a, p - 2, p); }   int arr[2000005] = {0};   int foo(int n) {     int maxsize = -1, startindex;     int sumleft[n];     int min, max;     int i;     sumleft[0] = ((arr[0] == 0) ? -1 : 1);     min = arr[0];     max = arr[0];     for (i = 1; i < n; i++) {       sumleft[i] = sumleft[i - 1] + ((arr[i] == 0) ? -1 : 1);       if (sumleft[i] < min) min = sumleft[i];       if (sumleft[i] > max) max = sumleft[i];     }     int hash[max - min + 1];     for (i = 0; i < max - min + 1; i++) hash[i] = -1;     for (i = 0; i < n; i++) {       if (sumleft[i] == 0) {         maxsize = i + 1;         startindex = 0;       }       if (hash[sumleft[i] - min] == -1)         hash[sumleft[i] - min] = i;       else {         if ((i - hash[sumleft[i] - min]) > maxsize) {           maxsize = i - hash[sumleft[i] - min];           startindex = hash[sumleft[i] - min] + 1;         }       }     }     if (maxsize == -1) maxsize = 0;     return maxsize;   }   int main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     int n;     cin >> n;     string s;     cin >> s;     for (int i = 0; i < n; i++) {       if (s[i] ==  1 ) arr[i] = 1;     }     cout << foo(n);     return 0;   }   