使用非递归的方式实现归并排序

话不多说，直接上代码：

public class MergySort {

    public static void main(String[] args) {
        int[] nums = {38, 27, 43, 3, 9, 82, 10};
        int[] sortedArray = MergySort.mergySort(nums);

        // 输出排序后的数组
        for (int num : sortedArray) {
            System.out.print(num + " ");
        }
    }

    public static int[] mergySort(int[] nums) {
        int n = nums.length;
        Queue<int[]> queue = new LinkedList<>();
        int[] ans ;

        for (int i = 0;i < n;i++) {
            queue.offer(new int[]{nums[i]});
        }

        while(queue.size() > 1) {
            int[] arr1 = queue.poll();
            int[] arr2 = queue.poll();
            int[] tmp = mergy(arr1,arr2);
            queue.offer(tmp);
        }

        ans = queue.poll();
        return ans;


    }


    public static int[] mergy(int[] arr1,int[] arr2) {
        int n1 = arr1.length;
        int n2 = arr2.length;
        int ptr1 = 0;
        int ptr2 = 0;
        int ansPtr = 0;
        int[] ans = new int[n1+n2];

        while(ptr1 < n1 && ptr2 < n2) {
            if (arr1[ptr1] <= arr2[ptr2]) {
                ans[ansPtr++] = arr1[ptr1++];
            } else {
                ans[ansPtr++] = arr2[ptr2++];
            }
        }

        while(ptr1 < n1) {
            ans[ansPtr++] = arr1[ptr1++];
        }

        while(ptr2 < n2) {
            ans[ansPtr++] = arr2[ptr2++];
        }

        return ans;
    }


}

基本思路是模拟我们递归实现归并的过程，大家可以把它理解成是一个自底向上的调用过程，用一个队列来模拟过程：

整个过程其实也是类似于广搜的过程。