【归并排序】Acwing787.归并排序

Acwing787.归并排序

题解

归并排序：采用分治思想，将左右完成排序，再进行一个归并，用左右得出整体的结果

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

const int N = 100010;

int q[N],tmp[N];

void merge_sort(int l, int r)
{
    if( l == r) return;
    int mid = l + r >> 1;
    merge_sort(l, mid);
    merge_sort(mid + 1, r);
    int i = l, j = mid + 1, k = l;
    while(i <= mid && j <= r)
        tmp[k ++ ] = q[i] < q[j] ? q[i ++ ] : q[j ++ ];
    while(i <= mid)
        tmp[k ++ ] = q[i ++ ];
    while(j <= r)
        tmp[k ++ ] = q[j ++ ];
    for(int x = l; x < k; ++x) q[x] = tmp[x];
}

int main()
{
    int n;
    scanf("%d",&n);
    for(int i = 0; i < n; ++i)
        scanf("%d",&q[i]);
    merge_sort(0, n - 1);
    for(int i = 0; i < n; ++i)
        printf("%d ",q[i]);
    return 0;
}
``