[Leetcode] Find the Duplicate number

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 element must exist. Assume that there are only one duplicate number, find the duplicate one.

Note:

1. You must the Modify the array (assume the array was read only).
2. You must use only constant extra space.
3. Your runtime complexity should is less than O(n2) .

Two-point lookup, Complexity O (NLOGN).

1 classSolution {2  Public:3     intFindduplicate (vector<int>&nums) {4         intL =0, r = nums.size ()-1, M;5          while(L <=r) {6m = L + ((r-l) >>1);7             intCNT =0;8              for(Auto A:nums)if(a <= m) + +CNT;9             if(CNT <= m) L = m +1;Ten             Elser = M-1; One         } A         returnl; -     } -};

[Leetcode] Find the Duplicate number