题目描述
归并排序
算法1
#include<iostream>
#include<cstdio>
using namespace std;
int n;
const int N = 100010;
int a[N],temp[N];
void merge_sort(int a[], int l, int r)
{
if(l >= r) return;
int mid = l+r>>1;
merge_sort(a, l, mid);
merge_sort(a, mid+1, r);
int i = l, j = mid + 1, k=0;//j的赋值
while(i <= mid && j <= r){
if(a[i] <= a[j]){
temp[k++] = a[i++];
}
else temp[k++] = a[j++];
}
//注意数组余下的一段也要复制
//要用while!!!不要写成if
while(i <= mid) temp[k++] = a[i++];
while(j <= r) temp[k++] = a[j++];
for(int i=l,j=0; i<=r; i++,j++) a[i] = temp[j];
}
int main()
{
scanf("%d",&n);
for(int i=0; i<n; i++) scanf("%d",&a[i]);
merge_sort(a,0,n-1);
for(int i=0; i<n; i++) printf("%d ",a[i]);
return 0;
}