LeetCode 945. Minimum Increment to Make Array Unique (javascript)

Given an array of integers A, a move consists of choosing any A[i], and incrementing it by 1.

Return the least number of moves to make every value in A unique.

Example 1:

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

Example 2:

Input: [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.

Note:

1. 0 <= A.length <= 40000
2. 0 <= A[i] < 40000

Solution:

/**
 * @param {number[]} A
 * @return {number}
 */
var minIncrementForUnique = function(A) {
    // sort array first!
    A.sort((a, b) => a - b);
    let ans = 0;
    for (let i = 1; i < A.length; i++) {
        // skip if A[i] > A[i - 1], no need to change
        if (A[i] > A[i - 1]) continue;
        // when A[i] >= A[i - 1] after previous modification
        // record how many move to make them unique
        ans += (A[i - 1] - A[i]) + 1;
        // make A[i] slightly bigger than A[i - 1]
        A[i] = A[i - 1] + 1;
    }
    return ans;
};