1460. Number Of Substrings Containing All Three Characters¶

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1460. Number of Substrings Containing All Three Characters

Medium

Given a string s consisting only of characters a, b and c.

Return the number of substrings containing at least one occurrence of all these characters a, b and c.

Example 1:

Input: s = "abcabc"
Output: 10
Explanation: The substrings containing at least one occurrence of the characters a, b and c are "abc", "abca", "abcab", "abcabc", "bca", "bcab", "bcabc", "cab", "cabc" and "abc" (again). 

Example 2:

Input: s = "aaacb"
Output: 3
Explanation: The substrings containing at least one occurrence of the characters a, b and c are "aaacb", "aacb" and "acb". 

Example 3:

Input: s = "abc"
Output: 1

Constraints:

• 3 <= s.length <= 5 x 10^4
• s only consists of a, b or c characters.

Solution¶

class Solution {
    public int numberOfSubstrings(String s) {
        int n = s.length();
        HashMap<Character, Integer> map = new HashMap<>();
        int left = 0 , right = 0;
        int count = 0;
        while (left < n) {
            while (right < n && map.size() < 3) {
                map.put(s.charAt(right) , map.getOrDefault(s.charAt(right) , 0) + 1);
                right++;
            }
            if(map.size() == 3) count += s.length() - (right) + 1;
            map.put(s.charAt(left) , map.getOrDefault(s.charAt(left) , 0) -1);
            if (map.get(s.charAt(left)) == 0) map.remove(s.charAt(left));
            left++;
        }
        return count;
    }
}

Complexity Analysis¶

• Time Complexity: O(?)
• Space Complexity: O(?)

Approach¶

Detailed explanation of the approach will be added here