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 {
   int numberOfSubstrings(string s) {
      int ret = 0;
      map <char, int> m;
      int j = 0;
      for(int i = 0; i < s.size(); i++){
         while(m['a'] > 0 && m['b'] > 0 && m['c'] > 0){
         ret += j;
      return ret;
   Solution ob;
   cout << (ob.numberOfSubstrings("abcabc"));





Updated on: 29-Apr-2020


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