寻找排列

/*
 * Leetcode Problem 484: Find Permutation
 * The problem statement: Given a string s that consists of only 'I' (increase) and 'D' (decrease), find a permutation of the first n positive integers that satisfy the given input string s.
 * 
 * Approach using Java Streams:
 * 1. Create a list to represent the initial sequence from 1 to n+1.
 * 2. Use a loop to traverse the input string 's'.
 * 3. For each 'I', reverse the sequence of the numbers collected so far.
 * 4. For 'D', continue collecting the numbers.
 * 5. Convert the list to an array and return the result.
 */
 
import java.util.*;
import java.util.stream.*;
 
public class FindPermutationStream {
    public int[] findPermutation(String s) {
        int n = s.length();
        List<Integer> result = IntStream.rangeClosed(1, n + 1).boxed().collect(Collectors.toList());
 
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) == 'I') {
                Collections.reverse(result.subList(0, i + 1));
            }
        }
        return result.stream().mapToInt(Integer::intValue).toArray();
    }
}