题目描述
样例
数据范围
1≤n≤100000
输入样例:
5
3 1 2 4 5
输出样例:
1 2 3 4 5
归并排序
时间复杂度 $O(nlogn)$
C++ 代码
#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 1e6 + 10;
int n;
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 cnt = 0;
int i = l, j = mid + 1;
while(i <= mid && j <= r)
if(q[i] <= q[j]) tmp[cnt ++] = q[i ++];
else tmp[cnt ++] = q[j ++];
while(i <= mid) tmp[cnt ++] = q[i ++];
while(j <= r) tmp[cnt ++] = q[j ++];
//在本次递归层数中将tmp中的元素赋值到q中
//memcpy(q + l, tmp, sizeof(int) * (r - l + 1)); //这句也行
for(i = l, j = 0; i <= r; i ++, j ++ ) q[i] = tmp[j];
}
int main(){
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;
}