-
Notifications
You must be signed in to change notification settings - Fork 1
/
FindDuplicateNumber.java
62 lines (51 loc) · 1.64 KB
/
FindDuplicateNumber.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
package com.leetcode;
import java.util.Arrays;
public class FindDuplicateNumber {
//https://leetcode.com/problems/find-the-duplicate-number/
class Solution {
public int findDuplicate(int[] nums) {
int n = nums.length;
int l = 1;//[1,n] number to search
int r = n-1;
while(l<= r){
int mid = l + (r-l)/2;//mid is potential number not index
int count = count(nums,mid);//no of elements that are < mid
if(count <= mid){
l = mid + 1;
}else{
// we have more numbers > mid so look for a number in [l,mid)
r = mid - 1 ;
}
}
return r+1;
}
public int count(int[] nums , int target){
int result = 0;
for(int n : nums){
if(n <= target) result++;
}
return result;
}
}
}
// note
/*
//binary search on value will not work because number may repeat many time 1,3,3,4,5 or 2,2,3,4,5 so binary search will miss 3 and 2 respectively
// Other test case possible to have 2,2,2,1 or 1,1,2,2 where more than one duplicate in test cases
public int findDuplicate(int[] nums) {
Arrays.sort(nums);
int n = nums.length;
int l = 0;
int r = n-1;
while(l<=r){
int mid = l + (r-l)/2;//index
if(nums[mid] == mid+1){
//search right
l = mid+1;
}else{
r = mid-1;
}
}
return (r>=0)?nums[r+1] : nums[0];
}
*/