Binary String [MEDIUM]

Company:Amazon

Question:

Given a binary string, count number of substrings that start and end with 1. For example, if the input string is “00100101”, then there are three substrings “1001”, “100101” and “101”.
 

Input:

The first line of input contains an integer T denoting the number of test cases.
Each test case consist of an integer 'n' denoting the string length and next line is followed by a binary string .

Output:

Print the number of substring starting and ending with 1 in a separate line.

Constraints:

1 ≤ T ≤ 40
1 ≤ |s| ≤ 1000

Example:

Input:
1
4
1111
Output:
6

CODE:

import java.util.*;

import java.lang.*;

import java.io.*;

class GFG {

public static void main (String[] args) {

Scanner sc = new Scanner (System.in);

int m = sc.nextInt();

for(int mi=0;mi<m;mi++){

   int n = sc.nextInt();

   String s= sc.next();

   int count=0;

   char c[]= s.toCharArray();

   for(int i=0;i<n;i++){

       if(c[i]=='1'){count++;}

   }

   System.out.println(Comb(count));

}

}

public static int Comb(int n){

   int temp=n*(n-1);

   return temp/2;

}

}

Explanation: If you observe carefully , the output is nC2 wherein n is number of 1s in the string. So now this is actually not a Medium level problem but just a easy/basic level problem.

EXECUTION TIME:0.11s