LC.P287[寻找重复数]

方法一：快慢指针

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class Solution {
    public int findDuplicate(int[] nums) {
        int slow = nums[0], fast = nums[nums[0]];
        while (slow != fast) {
            slow = nums[slow];
            fast = nums[nums[fast]];
        }
        slow = 0;
        while (slow != fast) {
            slow = nums[slow];
            fast = nums[fast];
        }
        return slow;
    }
}
  • 时间复杂度：$O(n)$
  • 空间复杂度：$O(1)$