Non-recursive version of mergesort

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Non-recursive version of merge sort, omitting the middle of the stack space, direct application period O (n) to the address space, so the space complexity is O (n), the time complexity is O (nlogn);

Algorithm idea:

　　For a start at intervals of merging, that is, the first element merge with the second one. The third and fourth for merging;

　　Then, at intervals of 2 to perform merging, merging 1-4, 5-8 merge;

　　And then at intervals of 2 * 2. Similarly, up to know more than the array length 2 * k.

while(i<length){
        Merge(arr,temp,i,length);
        i *= 2;
    }

　　When the two groups merge is not enough, if more than k elements, still be merged; if the remaining elements of no more than k elements, then copied directly to the middle of the array.

while(i <= length-2*k){
        sort(arr1,temp,i,i+k-1,i+2*k-1);
        i += 2*k;
    }

　

if(i < length-k+1)//如过剩余个数比一个k长度还多...那么就在进行一次合并
        sort(arr1,temp,i,i+k-1,length-1);
    else
        for(j=i;j<length;j++)
            temp[j] = arr1[j];

The main code:

void MergeSort(int *arr,int length){
    int *temp = (int *)malloc(sizeof(int)*length);
    int i = 1;
    while(i<length){
        Merge(arr,temp,i,length);
        i *= 2;
    }
}
void Merge(int *arr1,int *temp,int k,int length){
    int i = 0,j;
    while(i <= length-2*k){
        sort(arr1,temp,i,i+k-1,i+2*k-1);
        i += 2*k;
    }
    if(i < length-k+1)//如过剩余个数比一个k长度还多...那么就在进行一次合并
        sort(arr1,temp,i,i+k-1,length-1);
    else
        for(j=i;j<length;j++)
            temp[j] = arr1[j];
    for(i=0;i<length;i++){
        arr1[i] = temp[i];
    }
}
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] = {4,3,7,8,0,9,1,2,6,5};
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 Merge(int *arr1,int *temp,int k,int length);
void sort(int *arr3,int *arr1,int begin,int m,int end);
int main(){
    int Arr[10],i;
    copy(arrtest1,Arr,10);
    print(Arr,10);
    MergeSort(Arr,10);
    print(Arr,10);
    getchar();
    return 0;
}
void MergeSort(int *arr,int length){
    int *temp = (int *)malloc(sizeof(int)*length);
    int i = 1;
    while(i<length){
        Merge(arr,temp,i,length);
        i *= 2;
    }
}
void Merge(int *arr1,int *temp,int k,int length){
    int i = 0,j;
    while(i <= length-2*k){
        sort(arr1,temp,i,i+k-1,i+2*k-1);
        i += 2*k;
    }
    if(i < length-k+1)//如过剩余个数比一个k长度还多...那么就在进行一次合并
        sort(arr1,temp,i,i+k-1,length-1);
    else
        for(j=i;j<length;j++)
            temp[j] = arr1[j];
    for(i=0;i<length;i++){
        arr1[i] = temp[i];
    }
}
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");
}

Running instance:

Reproduced in: https: //my.oschina.net/u/204616/blog/545448