归并排序模版

#include <iostream>
using namespace std;
int n;
const int N = 1e6+10;
int q[N],tmp[N];
void merge_sort(int l,int r,int q[]){
    if(l>=r) return;
    int mid =l+r>>1;
    merge_sort(l,mid,q);
    merge_sort(mid+1,r,q);
    //归并的的过程
    int k=0,i=l,j=mid+1;
    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++];
    while(j<=r) tmp[k++]=q[j++];
    
    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,q);
    for(int i=0;i<n;i++){
        printf("%d ",q[i]);
    }
}

快排和二分

 

#include <iostream>
using namespace std;
const int N = 100010;
int n,m;
void quick_sort(int l,int r,int p[]){
    if(l>=r) return;
    int i=l-1,j=r+1;
    int x=p[i+j>>1];
    while(i<j){
        do i++;while(p[i]<x);
        do j--;while(p[j]>x);
        if(i<j) swap(p[i],p[j]);
    }
    quick_sort(l,j,p);
    quick_sort(j+1,r,p);
}
int main()
{
    scanf("%d", &n);
    int p[n];
    for (int i = 0; i < n; i ++ ){
        scanf("%d", &p[i]);
    }
    quick_sort(0,n-1,p);
    scanf("%d",&m);
    int x;
    for(int i=0;i<m;i++){
        scanf("%d", &x);
        int l=0,r=n-1;
        while(l<r){
            int mid=l+r >>1;
            if(p[mid]>=x) r=mid;
            else l=mid+1;
        }
        if(p[l]!=x) printf("NO\n");
        // else{
        //     int l=0,r=n-1;
        //     while(l<r){
        //         int mid=l+r+1 >> 1;
        //         if(p[mid]<=x) l=mid;
        //         else r=mid-1;
        //     }
        // }
        else{
            printf("YES\n");
        }
    }
        
    
}