287. Find the Duplicate Number

 

https://leetcode.com/problems/linked-list-cycle-ii/discuss/44777/Concise-JAVA-solution-based-on-slow-fast-pointers

fast slow， 刚开始全部初始化为0，当作起始点

 

class Solution {
    public int findDuplicate(int[] nums) {
        if(nums.length <= 1) return -1;
        int slow = nums[0];
        int fast = nums[nums[0]];
        while(slow != fast){
            slow = nums[slow];
            fast = nums[nums[fast]];
        }
        fast = 0;
        while(fast != slow){
            fast = nums[fast];
            slow = nums[slow];
        }
        return fast;
        
    }
}