Leetcode - Find the Duplicate Number
https://leetcode.com/problems/find-the-duplicate-number/
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:
- You must not modify the array (assume the array is read only).
- You must use only constant, O(1) extra space.
- Your runtime complexity should be less than O(n2).
- There is only one duplicate number in the array, but it could be repeated more than once.
func findDuplicate(nums []int) int {
if len(nums) <= 0 {
return -1
}
slow := nums[0]
fast := nums[nums[0]]
for slow != fast {
slow = nums[slow]
fast = nums[nums[fast]]
}
fast = 0
for fast != slow {
fast = nums[fast]
slow = nums[slow]
}
return slow
}
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