归并排序

归并排序

#include <iostream>
#include<stdio.h>
using namespace std;

const int N = 1e6 + 10;

int q[N], tmp[N];//借用临时数组来存储，最后再返还

void merge_sort(int q[], int l, int r)
{
    if (l >= r) return;

    int mid = l + r >> 1;//先确定分界点，中间值

    merge_sort(q, l, mid), merge_sort(q, mid + 1, r);//递归排序，排左右两边

    int k = 0, i = l, j = mid + 1;//不是1，是L
    while (i <= mid && j <= r)
        if (q[i] <= q[j]) tmp[k ++ ] = q[i ++ ];
        else tmp[k ++ ] = q[j ++ ];
    while (i <= mid) tmp[k ++ ] = q[i ++ ];//哪一个已经排完了剩下的直接放到后面
    while (j <= r) tmp[k ++ ] = q[j ++ ];

    for (i = l, j = 0; i <= r; i ++, j ++ ) q[i] = tmp[j];//返还给q
}

int main()
{
    int n;
    scanf("%d", &n);
    for (int i = 0; i < n; i ++ ) scanf("%d", &q[i]);

    merge_sort(q, 0, n - 1);

    for (int i = 0; i < n; i ++ ) printf("%d ", q[i]);

    return 0;
}

归并排序

原文：https://www.cnblogs.com/acm-walker/p/12859849.html