LeetCode 2489: Number of Substrings With Fixed Ratio Solution

Master LeetCode problem 2489 (Number of Substrings With Fixed Ratio), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

2489. Number of Substrings With Fixed Ratio

Medium

Hash Table Math String Prefix Sum

Problem Explanation

Explanation:

Given a string of digits and a fixed ratio, we need to find the number of substrings with a fixed ratio. A substring is considered valid if the ratio of the number of 0's to the number of 1's is equal to the fixed ratio.

To solve this problem, we can iterate through all possible substrings of the input string and check if the ratio of 0's to 1's in each substring matches the fixed ratio. We can keep track of the count of valid substrings and return it as the result. :

Solution Code

class Solution {
    public int countSubstrings(String s, int ratio) {
        int count = 0;
        for (int i = 0; i < s.length(); i++) {
            int zeros = 0, ones = 0;
            for (int j = i; j < s.length(); j++) {
                if (s.charAt(j) == '0') {
                    zeros++;
                } else {
                    ones++;
                }
                if (zeros != 0 && ones != 0 && zeros * ratio == ones) {
                    count++;
                }
            }
        }
        return count;
    }
}

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