(Recursive version) merge sort

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Recursive version of merge sort, time complexity is O (nlogn), the spatial complexity is O (n + logn);

Algorithm idea:

　　Ideas of using the autonomous, the sorting into two, each internal order, then traverse the sorted once can, a recursive call to the process.

The main code:

void MergeSort(int *arr,int length){
    Msort(arr,arr,0,length-1); 
}
void Msort(int *arr1,int *arr2,int begin,int end){
    int arr3[10];
    int m;
    if(begin == end)
        arr2[begin] = arr1[end];
    else{
        m = (end + begin)/2;
        Msort(arr1,arr3,begin,m);
        Msort(arr1,arr3,m+1,end);
        sort(arr3,arr2,begin,m,end);
    }
}
void sort(int *arr3,int *arr1,int begin,int m,int end){
    int i=begin,j=m+1,k,h;
    for(k=i; i<=m && j<=end;k++){
        if(arr3[i] < arr3[j])
            arr1[k] = arr3[i++];
        else
            arr1[k] = arr3[j++];
    }
    if(i <= m){
        for(h=0; h<=m-i;h++)
            arr1[k+h] = arr3[i+h];
    }else{
        for(h=0; h<=end-j;h++)
            arr1[k+h] = arr3[j+h];
    }
}

All Code:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int arrtest1[10] = {3,4,7,8,0,9,1,2,6,5};
int arrtest2[10] = {0,1,2,3,4,5,6,7,8,9};
int arrtest3[10] = {9,8,7,6,5,4,3,2,1,0};
void copy(int *from,int *arr,int length);
void print(int *arr,int length);
void MergeSort(int *arr,int length);
void Msort(int *arr1,int *arr2,int begin,int end);
void sort(int *arr3,int *arr1,int begin,int m,int end);
int main(){
    clock_t start,end;
    int Arr[10];
    int i;
    copy(arrtest1,Arr,10);
    print(Arr,10);
    MergeSort(Arr,10);
    print(Arr,10);
    start = clock();
    for(i=0;i<100000;i++){
        copy(arrtest1,Arr,10);
        //print(Arr,10);
        MergeSort(Arr,10);
        //print(Arr,10);
    }
    end = clock();
    printf("first test:%d\n",end-start);

    start = clock();
    for(i=0;i<100000;i++){
        copy(arrtest2,Arr,10);
        //print(Arr,10);
        MergeSort(Arr,10);
        //print(Arr,10);
    }
    end = clock();
    printf("first test:%d\n",end-start);

    start = clock();
    for(i=0;i<100000;i++){
        copy(arrtest3,Arr,10);
        //print(Arr,10);
        MergeSort(Arr,10);
        //print(Arr,10);
    }
    end = clock();
    printf("first test:%d\n",end-start);
    
    getchar();
    return 0;
}
void MergeSort(int *arr,int length){
    Msort(arr,arr,0,length-1); 
}
void Msort(int *arr1,int *arr2,int begin,int end){
    int arr3[10];
    int m;
    if(begin == end)
        arr2[begin] = arr1[end];
    else{
        m = (end + begin)/2;
        Msort(arr1,arr3,begin,m);
        Msort(arr1,arr3,m+1,end);
        sort(arr3,arr2,begin,m,end);
    }
}
void sort(int *arr3,int *arr1,int begin,int m,int end){
    int i=begin,j=m+1,k,h;
    for(k=i; i<=m && j<=end;k++){
        if(arr3[i] < arr3[j])
            arr1[k] = arr3[i++];
        else
            arr1[k] = arr3[j++];
    }
    if(i <= m){
        for(h=0; h<=m-i;h++)
            arr1[k+h] = arr3[i+h];
    }else{
        for(h=0; h<=end-j;h++)
            arr1[k+h] = arr3[j+h];
    }
}
void copy(int *from,int *arr,int length){
    int i;
    for(i=0;i<length;i++){
        arr[i] = from[i];
    }
}

void print(int *arr,int length){
    int i;
    for(i=0;i<length;i++){
        printf("%d ",arr[i]);
    }
    printf("\n");
}

Run the sample:

Reproduced in: https: //my.oschina.net/u/204616/blog/544967