排序

快速排序

#include<iostream>
using namespace std;
int nums[100];

 void quicksort(int num[],int left,int right)
{
    if(left>=right)
    return;
    int target=nums[left];
    int i=left-1,j=right+1;
    while(i<j)
    {
        do
            i++;
        while(nums[i]<target);
        do
            j--;
        while(nums[j]>target);
        if(i<j)
        swap(nums[i],nums[j]);
    }
    quicksort(nums,left,j);
    quicksort(nums,j+1,right);
}

int main()
{
    int n;
    cin>>n;
    for(int i=0;i<n;i++)
    cin>>nums[i];
    quicksort(nums,0,n-1);
    for(int i=0;i<n;i++)
    cout<<nums[i]<<" ";
}

 

归并排序

#include<iostream>
#include<algorithm>
#include<cmath>
using namespace std;

const int N=100000;
int n;
int nums[N],tmp[N];

void mergesort(int nums[],int left,int right)
{
    if(left>=right)        return;
    int mid=floor((left+right)/2);
    mergesort(nums,left,mid),mergesort(nums,mid+1,right);
    
    int k=0,p=left,q=mid+1;
    while(p<=mid&&q<=right)
    {
        if(nums[p]<=nums[q])
        tmp[k++]=nums[p++];
        else
        tmp[k++]=nums[q++];
    }
    
    while(p<=mid)    tmp[k++]=nums[p++];
    while(q<=right)        tmp[k++]=nums[q++];
    for(int i=left,k=0;i<=right;i++,k++)        nums[i]=tmp[k];
}

int main()
{
    scanf("%d",&n);
    for(int i=0;i<n;i++)    scanf("%d",&nums[i]);
    mergesort(nums,0,n-1);
    for(int i=0;i<n-1;i++)    cout<<nums[i]<<" ";
    cout<<nums[n-1];
    cout<<endl;
    return 0;
}