归并排序

import java.util.Arrays;

public class Merge {
    public int[] sort(int[] arr){
        if(arr.length < 2){
            return arr;
        }
        int middle = arr.length / 2;  //每次在中间将数组分割
        int[] left = Arrays.copyOfRange(arr, 0, middle);
        int[] right = Arrays.copyOfRange(arr, middle, arr.length);
        return merge(sort(left), sort(right));  //合并分割的数组
    }

    public int[] merge(int[] left, int[] right){  //合并数组
        int[] result = new int[left.length + right.length];
        int i = 0;
        while(left.length > 0 && right.length > 0){
            if(left[0] <= right[0]){
                result[i++] = left[0];
                left = Arrays.copyOfRange(left, 1, left.length);
            }else{
                result[i++] = right[0];
                right = Arrays.copyOfRange(right, 1, right.length);
            }
        }
        while(left.length > 0){
            result[i++] = left[0];
            left = Arrays.copyOfRange(left, 1, left.length);
        }
        while(right.length > 0){
            result[i++] = right[0];
            right = Arrays.copyOfRange(right, 1, right.length);
        }
        return result;
    }

    public static void main(String[] args) {
        int[] arr = {7,4,2,8,5};
        Merge merge = new Merge();
        int[] arrays = merge.sort(arr);
        for(int i = 0; i < arrays.length; i++){
            System.out.println(arrays[i]);
        }
    }
}