算法 -- 归并排序

归并算法(排序)

缺点：特消耗空间

代码

#pragma once

#include <stdlib.h>
#include <stdio.h>

class MergerSort
{
public:
    MergerSort(void);
    ~MergerSort(void);
public:
    void breakOut(int *arr, const int first, const int mid, const int last);
    void mergeSort(int *array, const int first, const int last);

    void print(const int first, const int len, const int *arr);
};

MergerSort::MergerSort(void)
{
}
MergerSort::~MergerSort(void)
{
} 

void MergerSort::breakOut(int *arr, const int first, const int mid, const int last)
{
    int* tmp;
    tmp = (int*)malloc((last-first+1)*sizeof(int));
    if(tmp == NULL) 
        return;

    int fir1 = first;
    int last1 = mid;
    int fir2 = mid+1;
    int last2 = last;
    int index = 0;
    while( (fir1<=last1) && (fir2<=last2))
    {
        if(arr[fir1] < arr[fir2])
        {
            tmp[index++] = arr[fir1++];
        } 
        else
        {
            tmp[index++] = arr[fir2++];
        }
    }
    while( fir1 <= last1)
        tmp[index++] = arr[fir1++];
    while( fir2 <= last2)
        tmp[index++] = arr[fir2++];
    for(int i=0; i<(last-first+1); i++)
    {
        arr[first+i] = tmp[i];
    }
    free(tmp);
}
void MergerSort::mergeSort(int *array, const int first, const int last)
{
    int mid=0;
    if(first < last)
    {
        mid=(first+last)/2;
        mergeSort(array,first,mid);
        mergeSort(array,mid+1,last);
        breakOut(array,first,mid,last);
        print(first, last-first+1, array+first);
    }
}

void MergerSort::print(const int first, const int len, const int *arr)
{
    static int count = 0;
    printf("(%2d)", count++);
    for(int i=0; i<first; i++)
    {
        printf("    ");
    }
    for(int i=0; i<len; i++)
    {
        printf("%3d ", arr[i]);
    }
    printf("\n");
}