部分排序

/*
 * Problem: Given an integer array, write a function to find the indices m and n such that if you sort the elements from index m to n, the entire array becomes sorted. The function should return [m, n], and if no such m and n exist (i.e., the array is already sorted), return [-1, -1].
 * Example: Input: [1, 2, 4, 7, 10, 11, 7, 12, 6, 7, 16, 18, 19]
 *          Output: [3, 9]
 */
import java.util.*;
import java.util.stream.*;

public class SolutionStream {
    public int[] findUnsortedSubarray(int[] nums) {
        if (nums == null || nums.length <= 1) return new int[]{-1, -1};
        int n = nums.length;

        int[] sorted = Arrays.stream(nums).sorted().toArray();
        int start = IntStream.range(0, n).filter(i -> nums[i] != sorted[i]).findFirst().orElse(-1);
        if (start == -1) return new int[]{-1, -1}; // Array is already sorted
        int end = IntStream.range(0, n).map(i -> n - 1 - i).filter(i -> nums[i] != sorted[i]).findFirst().orElse(-1);

        return new int[]{start, end};
    }
}