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.
Solution: We will solve this using Two pointers the brute force solution would be looping twice to find the duplicate which will take O(n2).
class HackerHeap {
public int findDuplicate(int[] nums) {
int slow = 0;
int fast = 0;
do{
slow = nums[slow];
fast = nums[nums[fast]];
}while(slow!=fast);
int find =0;
while(find!=slow){
find = nums[find];
slow = nums[slow];
}
return find;
}
}