324. Wiggle Sort II

https://leetcode.com/problems/wiggle-sort-ii/

Problem

Given an unsorted array nums, reorder it such that nums[0] < nums[1] > nums[2] < nums[3]....

Example 1:

Input: nums = [1, 5, 1, 1, 6, 4]
Output: One possible answer is [1, 4, 1, 5, 1, 6].

Example 2:

Input: nums = [1, 3, 2, 2, 3, 1]
Output: One possible answer is [2, 3, 1, 3, 1, 2].

Note: You may assume all input has valid answer.

Follow Up: Can you do it in O(n) time and/or in-place with O(1) extra space?

Solution

class Solution {
public:
    void wiggleSort(vector<int>& nums) {
        const int n = nums.size();
        if (n < 2) return;
        vector<int> dump(nums);
        sort(dump.begin(), dump.end());
        int idx = -1;
        int i = (n - 1) / 2;
        int j = n - 1;
        for (int k = i; k >= 0; --k) {
            nums[++idx] = dump[k];
            if (j > i) nums[++idx] = dump[j--];
        }
    }
};

• #veryimportant

• #sorting