1 題目
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.
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.
Credits:
Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.
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2 代碼
public class Solution {
public int findDuplicate(int[] nums) {
if (nums == null || nums.length == 0) {
return 0;
}
int isDuplicate[] = new int[nums.length - 1];
for (int i = 0; i < nums.length; i++) {
if (isDuplicate[nums[i] - 1] ==1) {
return nums[i];
}else{
isDuplicate[nums[i] - 1]++;
}
}
return 0;
}
}