冒泡排序：
#include <iostream>
using namespace std;
int a[] = {5,3,2,1,4};
int main(){
    int n = 5;
    for(int i = 0 ; i < n ; i ++ ){
        for(int j = i + 1 ; j < n ; j ++ ){
            if(a[i] > a[j])swap(a[i], a[j]);
        }
    }
    for(int i = 0 ; i < n ; i ++ )cout << a[i] << " ";
    return 0;
}

选择排序：
#include <iostream>
using namespace std;
int a[] = {0,5,1,2,5};
int main(){
    int n = 5;
    for(int i = 0 ; i < n - 1 ; i ++ ){
        int mn = 10000 , l = 0;
        for(int j = i + 1 ; j < n ; j ++ ){
            if(a[j] < mn){
                mn = a[j];
                l = j;
            }
        }
        if(a[i] > a[l]){
            swap(a[i],a[l]);
        }
    }
    for(int i = 0 ; i < n ; i ++ )cout << a[i] << " ";
    return 0;
}

cin优化:
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);

计数排序:
#include <iostream>
#include <map>
using namespace std;
int a[] = {0,5,1,2,3};
map<int,int> mp;
int main(){
    int n = 5;
    for(int i = 0 ; i < n ; i ++ ){
        mp[a[i]] ++;
    }
    for(int i = 0 ; i <= 10000 ; i ++ ){
        if(mp[i] > 0){
            for(int j = 1 ; j <= mp[i] ; j ++ ){
                cout << i << " ";
            }
        }
    }
    return 0;
}

字符替换:
#include <iostream>
#include <cstring>
using namespace std;
string s;
char c;
int main(){
    cin >> s >> c;
    for(int i = 0 ; i < s.size() ; i ++ ){
        if(s[i] != c){
            cout << s[i];
        }
    }
    return 0;
}

交换（指针）
#include <bits/stdc++.h>
using namespace std;

int main()
{
    int a,b;
    cin >> a >> b;
    int *l = &a, *r = &b;;
    int *k = *l;
    *l = *r;
    *r = *k;
    cout << a << " " << b;
    return 0;
}

—— 本文来自火龙信奥（义乌睿码科技）：义乌青少年信息学奥赛与编程教育平台，专注 CSP-J/S、NOIP、GESP 竞赛培训，线上线下融合教学，助力编程升学。网址：hlcoding.com