Number of Substrings Containing All Three Characters in C++

Suppose we have given a string s consisting only of characters a, b and c. We have to return the number of substrings containing at least one occurrence of all these characters a, b and c. So for example, if the string is “abcabc”, then the output will be 10, as the substring containing at least one occurrence of the characters a, b and c, these are “abc”, “abca”, “abcab”, “abcabc”, “bca”, “bcab”, “cab”, “cabc” and “abc” (again for the last part).

To solve this, we will follow these steps −

• ret := 0, make a map called m, set j := 0

• for i in range 0 to size of s

  • increase count of s[i] in the map m

  • while m[‘a’] > 0 and m[‘b’] > 0 and m[‘c’] > 0,

    • decrease the count of s[i] in map m

    • increase j by 1

  • increase ret by j

• return ret

Example (C++)

Let us see the following implementation to get a better understanding −

 Live Demo

#include <bits/stdc++.h>
using namespace std;
class Solution {
public:
   int numberOfSubstrings(string s) {
      int ret = 0;
      map <char, int> m;
      int j = 0;
      for(int i = 0; i < s.size(); i++){
         m[s[i]]++;
         while(m['a'] > 0 && m['b'] > 0 && m['c'] > 0){
            m[s[j]]--;
            j++;
         }
         ret += j;
      }
      return ret;
   }
};
main(){
   Solution ob;
   cout << (ob.numberOfSubstrings("abcabc"));
}

Input

"abcabc"

Output

10