归并排序

归并排序采用递归和分治的思想。分治主要是将两个无序数组合并成一个有序数组。

# include <iostream>

using namespace std;

void MergeTwo(int sourceArr[],int tempArr[],int startIndex,int midIndex,int endIndex){//0,4,9
    int i = startIndex;
    int j = midIndex+1;
    int k = startIndex;
    while(i <= midIndex && j <= endIndex){
        if(sourceArr[i] > sourceArr[j])
            tempArr[k++] = sourceArr[j++];
        else
            tempArr[k++] = sourceArr[i++];
    }
    while(i <= midIndex)
        tempArr[k++] = sourceArr[i++];
    while(j <= endIndex + 1)
        tempArr[k++] = sourceArr[j++];
    for(i = startIndex ; i <= endIndex ; i++)
        sourceArr[i] = tempArr[i];
}

//内部使用递归
void MergeSort(int sourceArr[],int tempArr[],int startIndex,int endIndex){
    int midIndex;
    if(startIndex < endIndex){
        midIndex = (startIndex + endIndex)/2;
        MergeSort(sourceArr,tempArr,startIndex,midIndex);
        MergeSort(sourceArr,tempArr,midIndex+1,endIndex);
        MergeTwo(sourceArr,tempArr,startIndex,midIndex,endIndex);
    }
}

void Print(int arr[],int n){
    for(int i = 0 ; i < n ; i++)
        cout << arr[i] << endl;
}

int main(){
    int arr[10] = {123,4,23,3,4,67,78,4543,234,9768};
    int b[10];
    MergeSort(arr,b,0,9);
    Print(arr,10);
    return 0;
}