归并排序 图解算法过程

Posted 2022-12-12 XianMing的博客

本文转自：http://blog.csdn.net/collonn/article/details/17581953

图真好！

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归并排序，图解，详细过程。

package com.collonn.algorithm.sort;

/**
 * <pre>
 * 经典归并排序
 * </pre>
 */
public class MergeSort 

    public void mergeSort(int[] s, int start, int end) 
        if (start >= end) 
            return;
        

        int m = (start + end) / 2;
        int start1 = start;
        int end1 = m;
        int start2 = m + 1;
        int end2 = end;
        this.mergeSort(s, start1, end1);
        this.mergeSort(s, start2, end2);

        this.merge(s, start1, end1, start2, end2);
    

    // 合并两个有序数组为一个有序数组
    private void merge(int[] s, int start1, int end1, int start2, int end2) 
        System.out.printf("\\n开始合并,合并范围,[%d,%d],[%d,%d]", start1, end1, start2, end2);
        int start = start1;
        // 临时数组
        int[] t = new int[end2 - start1 + 1];
        // 临时数组下标
        int i = 0;

        // 比较开始
        while (start1 <= end1 && start2 <= end2) 
            if (s[start1] < s[start2]) 
                t[i] = s[start1];
                start1++;
                i++;
                continue;
            
            if (s[start1] > s[start2]) 
                t[i] = s[start2];
                start2++;
                i++;
                continue;
            
        

        // 拷贝剩余元素
        while (start1 <= end1) 
            t[i] = s[start1];
            start1++;
            i++;
        

        // 拷贝剩余元素
        while (start2 <= end2) 
            t[i] = s[start2];
            start2++;
            i++;
        

        // 将已排好序的元素放回对应位置
        for (i = 0; i < t.length; i++) 
            s[start + i] = t[i];
        

        // 打印数组
        PrintArray(s);
    

    // 打印数组
    private static void PrintArray(int[] s) 
        System.out.print("\\n下标:");
        for (int p = 0; p < s.length; p++) 
            System.out.printf("%2d,", p);
        
        System.out.print("\\n值值:");
        for (Integer m : s) 
            System.out.printf("%2d,", m);
        
        System.out.print("\\n-----------------------------");
    

    public static void main(String[] args) 
        // int[] s = new int[]  99, 88, 5, 99, 7, 9, 3, 8, 10, 90, 56, 83, 39, 22 ;
        int[] s = new int[]  9, 2, 3, 7, 6, 5, 8, ;

        // 打印数组
        PrintArray(s);

        MergeSort mergeSort = new MergeSort();
        mergeSort.mergeSort(s, 0, s.length - 1);

        // 打印数组
        PrintArray(s);
    

运程时输出如下：

下标: 0, 1, 2, 3, 4, 5, 6,

值值: 9, 2, 3, 7, 6, 5, 8,

开始合并,合并范围,[0,0],[1,1]
下标: 0, 1, 2, 3, 4, 5, 6,

值值: 2, 9, 3, 7, 6, 5, 8,

开始合并,合并范围,[2,2],[3,3]
下标: 0, 1, 2, 3, 4, 5, 6,

值值: 2, 9, 3, 7, 6, 5, 8,

开始合并,合并范围,[0,1],[2,3]
下标: 0, 1, 2, 3, 4, 5, 6,

值值: 2, 3, 7, 9, 6, 5, 8,

开始合并,合并范围,[4,4],[5,5]
下标: 0, 1, 2, 3, 4, 5, 6,

值值: 2, 3, 7, 9, 5, 6, 8,

开始合并,合并范围,[4,5],[6,6]
下标: 0, 1, 2, 3, 4, 5, 6,

值值: 2, 3, 7, 9, 5, 6, 8,

开始合并,合并范围,[0,3],[4,6]
下标: 0, 1, 2, 3, 4, 5, 6,

值值: 2, 3, 5, 6, 7, 8, 9,

下标: 0, 1, 2, 3, 4, 5, 6,

值值: 2, 3, 5, 6, 7, 8, 9,