LeetCode 945. Minimum Increment to Make Array Unique

原题链接在这里：https://leetcode.com/problems/minimum-increment-to-make-array-unique/

题目：

You are given an integer array nums. In one move, you can pick an index i where 0 <= i < nums.length and increment nums[i] by 1.

Return the minimum number of moves to make every value in nums unique.

The test cases are generated so that the answer fits in a 32-bit integer.

Example 1:

Input: nums = [1,2,2]
Output: 1
Explanation: After 1 move, the array could be [1, 2, 3].

Example 2:

Input: nums = [3,2,1,2,1,7]
Output: 6
Explanation: After 6 moves, the array could be [3, 4, 1, 2, 5, 7].
It can be shown with 5 or less moves that it is impossible for the array to have all unique values.

Constraints:

• 1 <= nums.length <= 105
• 0 <= nums[i] <= 105

题解：

Sort the array.

For each number, it should be at least prev + 1.

If not, then accumlate prev + 1 - nums[i] to the result.

Time Complexity: O(nlogn). n = nums.length.

Space: O(1).

AC Java:

class Solution {
    public int minIncrementForUnique(int[] nums) {
        if(nums == null || nums.length == 0){
            return 0;
        }
        
        Arrays.sort(nums);
        int res = 0;
        int prev = nums[0];
        for(int i = 1; i < nums.length; i++){
            int expect = prev + 1;
            res += Math.max(expect - nums[i], 0);
            prev = Math.max(expect, nums[i]);
        }
        
        return res;
    }
}