Codeforces Round #691 (Div. 2)A-C题

Div2第一次AC两道题

A题：
直接比较一张卡片上的两个数，blue大blue ,red大red ，最后比较（当时就凭感觉应该是这样qwq）

#include<iostream>
#include<stdio.h>
#include<string>
#include<algorithm>
using namespace std;

char r[1005];
char b[1005];

int main()
{
    int t;
    cin>>t;
    int n;
    int blue;
    int red;
    while(t--){
        cin>>n;
        red = blue = 0;
        for (int i = 1;i<=n;i  ){
            cin >> r[i];
        }
        for (int i = 1; i <= n;i  ){
            cin >> b[i];
        }
        for (int i = 1; i <= n;i  ){
            if((int)(r[i]-'0')>(int)(b[i]-'0'))
                red  ;
            if((int)(r[i]-'0')<(int)(b[i]-'0'))
                blue  ;
        }
        if (red > blue)
            cout<<"RED"<<endl;
        if(red<blue)
            cout << "BLUE" << endl;
        if(red==blue)
            cout << "EQUAL" << endl;
    }
    return 0;
}

 

---

B题：

一开始用dfs搜，明显超时，果断用dfs找规律

#include<iostream>
using namespace std;
//dfs打表wow
//前面是dfs搜的代码
/*
void dfs(int x,int y)
{
    if(num==n){
        if(!vis[x][y]){
            vis[x][y] = 1;
            sum  ;
        }
        return;
    }
    for (int i = 1;i<=2;i  ){
        if (flag)
        {
            num  ;
            flag = 0;
            dfs(x   1, y);
            num--;
            num  ;
            flag = 0;
            dfs(x - 1, y);
            num--;
            return;
        }
        else
        {
            num  ;
            flag = 1;
            dfs(x, y   1);
            num--;
            num  ;
            flag = 1;
            dfs(x, y - 1);
            num--;
            return;
        }
    }
}



int main()
{
    cin>>n;
    flag = 0;
    dfs(500,500);
    long long k=sum;
    cout << sum << endl;
    flag = 1;
    dfs(500, 500);
    cout<<sum-k<<endl;
    cout << sum;
    return 0;
}
*/

int main()
{
    int n;
    cin >> n;
    if(n%2==0){
        cout << (n / 2   1) * (n / 2   1);
        return 0;
    }else{
        n  ;
        cout << ((n / 2   1) * (n / 2   1) - (n / 2   1))*2;
        return 0;
    }
}

 

---

C题：（补题）

比赛时没做出来（其实是不会）

（数论一直搞不懂）

gcd(a,b)=gcd(a-b,b)

#include<iostream>
#include<stdio.h>
#include<algorithm>
using namespace std;


long long gcd(long long x,long long y)
{
    if(y==0)
        return x;
    else
        return gcd(y, x % y);
}
long long a[200006];

int main()
{
    int n;
    int m;
    long long t;
    long long gcd_x=1;
    cin >> n >> m;
    for(int i=1;i<=n;i  )
        cin>>a[i];
    sort(a   1, a   n   1);
    if(n>=2){
        gcd_x = a[2] - a[1];
        for (int i = 3; i <= n;i  )
            gcd_x=gcd(gcd_x,a[i]-a[i-1]);
        for (int i = 1;i<=m;i  ){
            cin>>t;
            cout << gcd(gcd_x, a[1]   t) << ' ';
        }
    }else{
        for (int i = 1; i <= m;i  ){
            cin >> t;
            cout << t   a[1] << ' ';
        }
    }
    return 0;
}

 

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