排序（Java）

問題描述

給定一個整型數組nums，nums中偶數位上的數爲增，奇數位上的數爲減。請將數組按照升序排序。
例:
輸入: nums = {1,8,3,6,5,4,7,2,9}
輸出：nums = {1,2,3,4,5,6,7,8,9}

public class MergeSort {
    public static void mergeSort(int[] nums) {
        int length = nums.length;
        int n1 = 0;//升序序列的長度
        int n2 = length/2;//降序序列的長度
        int i = 0;//升序序列的下標
        int j = 0;
        if(length%2 != 0){
            n1 = length/2+1;
            j = length -2;
        }else {
            n1 = length/2;
            j = length-1;
        }
        int[] nums1 = new int[n1];
        for(int k=0;k<n1;k++){
            nums1[k] = nums[i];
            i = i+2;
        }
        int[] nums2 = new int[n2];
        for(int k=0;k<n2;k++){
            nums2[k] = nums[j];
            j = j-2;
        }

        int m = 0;
        i=0;
        j=0;
        while(m<length && i<n1 && j<n2) {
            while(m<length && i<n1 && j<n2 && nums1[i] <= nums2[j]) {
                nums[m] = nums1[i];
                i++;
                m++;
            }
            while(m<length && i<n1 && j<n2 && nums1[i] > nums2[j]) {
                nums[m] = nums2[j];
                m++;
                j++;
            }
        }
        while(m<length && i<n1) {
            nums[m] = nums1[i];
            i++;
            m++;
        }
        while(m<length && j<n2) {
            nums[m] = nums2[j];
            m++;
            j++;
        }

    }
    public static void main(String[] args) {
        int[] nums = {1,39,5,21,7,18,12,9,18,2,32};
        mergeSort(nums);
        for(int i=0;i<nums.length;i++){
            System.out.print(nums[i]+" ");
        }

    }
}