归并算法

归并排序调用过程

#include <iostream>

using namespace std;

void merge_array(int* s,int begins,int mid, int ends, int* temp)
{
    int i = begins, j = mid+1, k = 0;
    while(i <= mid && j <= ends)
    {
        if(s[i] <= s[j])
            temp[k++] = s[i++];
        else
            temp[k++] = s[j++];
    }
    while(i <= mid)
        temp[k++] = s[i++];

    while(j <= ends)
        temp[k++] = s[j++];

    for(int i = 0; i < k; ++i) //要特别注意 排序后要写会原数组
        s[begins+i] = temp[i];
}

void merge_sort(int* s,int begins, int ends,int* temp)
{
    if(begins < ends)
    {
        int mid = (begins + ends) / 2;
        merge_sort(s, begins, mid, temp);
        merge_sort(s, mid+1, ends, temp);
        merge_array(s, begins, mid, ends, temp);
    }
}

int main()
{
    int s[20], n,temp[20];
    cin >> n;
    for(int i = 0; i < n; ++i)
        cin >> s[i];
    merge_sort(s, 0, n-1, temp);
    for(int i = 0; i < n; ++i)
        cout << s[i] << ' ';
    return 0;
}