how to find deuplicate numbers in array code example
Example: Find the duplicate in an array of N integers.
// 287. Find the Duplicate Number
// Medium
// 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.
class Solution {
public:
int findDuplicate(vector<int>& nums) {
int n=nums.size();
int s=nums[0];
int f=nums[nums[0]];
while(s!=f) {
s=nums[s];
f=nums[nums[f]];
}
f=0;
while(s!=f) {
s=nums[s];
f=nums[f];
}
return s;
}
};