[LC] 287. Find the Duplicate Number

标签：solution   mod   sum   sam   constant   must   int   fas   ast   

Given an array nums containing n + 1 integers where each integer is between 1 and n (inclusive), prove that at least one duplicate number must exist. Assume that there is only one duplicate number, find the duplicate one.

Example 1:

Input: [1,3,4,2,2]
Output: 2

Example 2:

Input: [3,1,3,4,2]
Output: 3

Note:

1. You must not modify the array (assume the array is read only).
2. You must use only constant, O(1) extra space.
3. Your runtime complexity should be less than O(n2).
4. There is only one duplicate number in the array, but it could be repeated more than once.

Same Algorithm with LC. 142

Time: O(N)

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

[LC] 287. Find the Duplicate Number

标签：solution   mod   sum   sam   constant   must   int   fas   ast   

原文地址：https://www.cnblogs.com/xuanlu/p/12067018.html