LC.P581[最短无序连续子数组]

方法一：排序+双指针

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class Solution {
    public int findUnsortedSubarray(int[] nums) {
        int[] arr = nums.clone();
        Arrays.sort(arr);
        int left = 0, right = nums.length - 1;
        while (left <= right && nums[left] == arr[left]) ++left;
        while (left <= right && nums[right] == arr[right]) --right;
        return right - left + 1;
    }
}
  • 时间复杂度：O(nlogn)
  • 空间复杂度：O(n)

方法二：一次遍历

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class Solution {
    public int findUnsortedSubarray(int[] nums) {
        int n = nums.length;
        int min = nums[n - 1], max = nums[0];
        int left = -1, right = -1;
        for (int i = 0; i < n; i++) {
            if (nums[i] < max) right = i;
            else max = nums[i];
            if (nums[n - i - 1] > min) left = n - i - 1;
            else min = nums[n - i - 1];
        }
        return right == -1 ? 0 : right - left + 1;
    }
}
  • 时间复杂度：O(n)
  • 空间复杂度：O(1)