AtCoder Beginner Contest 174

A - Air Conditioner

C++

#include<iostream>
#include<vector>
#include<algorithm>
#include<iomanip>
#include<utility>
#include<iomanip>
#include<map>
#include<queue>
#include<cmath>
#include<cstdio>

#define rep(i,n) for(int i=0; i<(n); ++i)
#define pai 3.1415926535897932384

using namespace std;
using ll =long long;
using P = pair<int,int>;

int main(int argc, const char * argv[]) {

    int X;
    cin >> X;

    if(X>=30) cout << "Yes" << endl;
    else cout << "No" << endl;

    return 0;
}

B - Distance

• 少数で何かあるといけないからPythonを使用

Python

import math

N, D = list(map(int, input().split()))

c=0
for i in range(0, N):
    X, Y = list(map(int, input().split()))
    if math.sqrt(X * X + Y * Y) <= D:
        c+=1

print(c)

C - Repsept

• 計算途中で余りを求めても同じ結果を返す法則があります

C++

#include<iostream>
#include<vector>
#include<algorithm>
#include<iomanip>
#include<utility>
#include<iomanip>
#include<map>
#include<queue>
#include<cmath>
#include<cstdio>

#define rep(i,n) for(int i=0; i<(n); ++i)
#define pai 3.1415926535897932384

using namespace std;
using ll =long long;
using P = pair<int,int>;

int K;

int main(int argc, const char * argv[]) {

    cin >> K;

    ll c=0;
    ll num=7;
    while(c<=K){
        c++;
        if(num%K==0){
            break;
        }
        num = num%K;
        num = (num * 10 + 7);
    }

    if(num%K==0) cout << c << endl;
    else cout << "-1" << endl;

    return 0;
}

D - Alter Altar

• 最後の要素からswapするだけです

C++

#include<iostream>
#include<vector>
#include<algorithm>
#include<iomanip>
#include<utility>
#include<iomanip>
#include<map>
#include<queue>
#include<cmath>
#include<cstdio>

#define rep(i,n) for(int i=0; i<(n); ++i)
#define pai 3.1415926535897932384

using namespace std;
using ll =long long;
using P = pair<int,int>;

char c[200000];

int main(int argc, const char * argv[]) {

    int N;
    cin >> N;
    cin >> c;

    int w=0;
    int count=0;
    for(int i=N-1; i>0; i--){
        if(c[i] == 'R'){
            while(w<N&&i>w){
                if(c[w]=='W'){
                    c[w] = c[i];
                    c[i] = 'W';
                    count++;
                    break;
                }
                w++;
            }
        }
    }

    cout << count << endl;

    return 0;
}