归并排序

归并排序的原理：查看此处

1.  C实现

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

const int NUM=10;
void mergeSort(int data[], int start, int end);
void merge(int data[], int start, int mid, int end);
void printArr(int arr[], int length);

void main(int argc, char *argv[]){
    int arr[NUM];
    int i;
    srand((int)time(NULL));
    for(i=0; i<NUM; i++){
        arr[i] = (int)(30*rand()/(RAND_MAX+1.0));
    }
    printArr(arr,NUM);
    mergeSort(arr, 0, NUM-1);
    printArr(arr, NUM);
}

void mergeSort(int data[], int start, int end){
    int mid;
    if(start < end){
        mid = (start+end)/2;
        mergeSort(data, start, mid);
        mergeSort(data, mid+1, end);
        merge(data, start, mid, end);
    }
}

void merge(int data[], int start, int mid, int end){
    int leftLength, rightLength;
    int *temp;
    int tempStart = start;
    int tempEnd = mid+1;
    int tempkey = 0;
    leftLength = mid - start + 1;
    rightLength = end-start;
    temp = (int *)malloc(sizeof(int) * (end-start+1));
    while(tempStart<=mid && tempEnd <= end){
        if(data[tempStart] > data[tempEnd]){
           temp[tempkey++] = data[tempEnd];
           tempEnd++;
        }else{
            temp[tempkey++] = data[tempStart];
            tempStart++;
        }
    }

    while(tempStart <= mid){
          temp[tempkey++] = data[tempStart++];
    }

    while(tempEnd <= end){
        temp[tempkey++] = data[tempEnd++];
    }
    tempkey = 0;

    while(start+tempkey<=end){
        data[start+tempkey] = temp[tempkey];
        tempkey++;
    }

    free(temp);
}
void printArr(int arr[], int length){
    int i;
    for(i=0; i<length; i++){
        printf("%d\t", arr[i]);
    }
}

 

2.PHP实现

<?php
$arr = range(1,100);
$arr = array_rand($arr, 30);
shuffle($arr);
print_r($arr);
print_r(mergeSort($arr));

function mergeSort(Array $arr){
    if(count($arr) == 1) return $arr;
    $mid = floor(count($arr)/2);
    return merge(mergeSort(array_slice($arr, 0, $mid)), mergeSort(array_slice($arr, $mid)));
}

function merge(Array $left, Array $right){
    $result = array();
    while(count($left) >0 && count($right) > 0){
        if($left[0] < $right[0]){
            array_push($result, array_shift($left));
        }else{
            array_push($result, array_shift($right));
        }
    }
    return array_merge($result, $left, $right);
}
?>

 

3.javascript实现

<script>
//生成一个随机数组
var esnum = Math.ceil(Math.random()*100);
var eArr = new Array(esnum);
for(var i=0; i<eArr.length; i++){
    eArr[i] = Math.round(Math.random() * 100);
}
alert(eArr);
alert(mergeSort(eArr));

function mergeSort(arr){
    if(arr.length == 1){
        return arr;
    }
    //求出分割终点
    var mid = Math.floor(arr.length/2);
    return merge(mergeSort(arr.slice(0,mid)), mergeSort(arr.slice(mid)));
}

function merge(left, right){
    var result = [];
    while(left.length !=0 && right.length !=0){
        if(left[0] < right[0]){
            result.push(left.shift());
        }else{
            result.push(right.shift());
        }
    }
    return result.concat(left).concat(right);
}
</script>