形成字符串的最短路径

/*
 * Problem 1055: Shortest Way to Form String
 * 
 * Given a string source and a string target, return the minimum number of subsequences of source such that their concatenation equals target. 
 * If the task is impossible, return -1.
 * 
 * Approach using Java Streams:
 * 1. Stream through the target string and try to match characters in the source using IntStream.
 * 2. Use nested IntStream loops to check for character matches.
 * 3. Return -1 if no progress is made in matching.
 */
import java.util.stream.IntStream;

public class Solution {
    public int shortestWay(String source, String target) {
        int[] result = {0};  // To store number of subsequences used
        int i = 0;  // Pointer for target
        while (i < target.length()) {
            int start = i;  // To track progress in target
            i = IntStream.range(i, target.length())
                    .filter(idx -> IntStream.range(0, source.length())
                    .anyMatch(j -> source.charAt(j) == target.charAt(idx)))
                    .findFirst()
                    .orElse(target.length());
            if (start == i) {  // No progress in target
                return -1;
            }
            result[0]++;
        }
        return result[0];
    }
}