统计只差一个字符的子串数目

// Java Stream solution

/*
 * This approach is not naturally suited to streams due to the need for nested loops
 * and mutable state. However, we can simulate the outer loop using IntStream and
 * then use a method to handle the inner logic.
 */

import java.util.stream.IntStream;

public class Solution {
    public int countSubstrings(String s, String t) {
        return IntStream.range(0, s.length())
                .map(i -> (int) IntStream.range(0, t.length())
                        .flatMap(j -> IntStream.range(0, Math.min(s.length() - i, t.length() - j))
                                .mapToObj(k -> new int[] {i, j, k}))
                        .filter(arr -> s.charAt(arr[0] + arr[2]) != t.charAt(arr[1] + arr[2])
                                && IntStream.range(0, arr[2])
                                .allMatch(k -> s.charAt(arr[0] + k) == t.charAt(arr[1] + k)))
                        .count())
                .sum();
    }
}