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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 −
#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
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