945. Minimum Increment to Make Array Unique

Description

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 numsunique.

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

 

Solutions

Solution: Greedy

• Time complexity: O(Max(nums))
• Space complexity: O(Max(nums))

 

JavaScript

/**
 * @param {number[]} nums
 * @return {number}
 */
const minIncrementForUnique = function (nums) {
  const max = Math.max(...nums);
  const counts = new Array(max + 1).fill(0);
  let result = 0;
  let next = 0;

  for (const num of nums) {
    counts[num] += 1;
  }
  for (let num = 0; num <= max; num++) {
    while (counts[num] > 1) {
      if (num > next) next = num + 1;

      while (next <= max && counts[next]) next += 1;

      result += next - num;

      if (next <= max) {
        counts[next] += 1;
      } else {
        next += 1;
      }
      counts[num] -= 1;
    }
  }
  return result;
};