PTA乙级1006~1010【c++】

1006 换个格式输出整数

#include <iostream>
using namespace std;

int main(){
	int n;
	cin >> n;
	int b = n / 100;
	int s = n / 10 % 10;
	int g = n % 10;
	for (int i = 0; i < b; i ++ ) cout << 'B';
	for (int i = 0; i < s; i ++ ) cout << 'S';
	for (int i = 0; i < g; i ++ ) cout << i + 1;
	return 0;
}

1007 素数对猜想

#include <iostream>
using namespace std;
const int N = 1e5 + 10;
bool st[N];
int p[N], cnt, res;

//素数筛 
void get_prime(int n){
	for (int i = 2; i <= n; i ++ ){
		if (!st[i]){
			p[cnt ++ ] = i;
			if (cnt > 1 && p[cnt - 1] - p[cnt - 2] == 2) res ++;
		}
		for (int j = 0; p[j] <= n / i; j ++ ){
			st[p[j] * i] = true;
			if (i % p[j] == 0) break;
		}
	}
}

int main(){
	int n;
	cin >> n;
	get_prime(n);
	cout << res;
	return 0;
}

其实没必要，纯纯暴力也能过：（如下）

#include <iostream>
using namespace std;

bool is_prime(int n){
	for (int i = 2; i <= n / i; i ++ ){
		if (n % i == 0) return false;
	}
	return true;
}

int main(){
	int n, t = 3, res = 0;
	cin >> n;
	for (int i = 3; i <= n; i ++ ){
		if (is_prime(i)){
			if (i - t == 2) res ++;
			t = i;
		}
	}	
	cout << res << endl;
	return 0;
}

1008 数组元素循环右移问题

不移动数组的版本：

#include <iostream>
using namespace std;

int main(){
	int n, m;
	cin >> n >> m;
	m %= n;
	int a[n];
	for (int i = 0; i < n; i ++ ) cin >> a[i];
	for (int i = n - m; i < n; i ++ ) cout << a[i] << ' ';
	for (int i = 0; i < n - m; i ++ ){
		if (i == n - m - 1) cout << a[i] << endl;
        else cout << a[i] << ' ';
	}
	return 0;
}

老老实实移动数组的版本：

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

int main(){
	int n, m;
	cin >> n >> m;
	m %= n;
	int a[n];
	for (int i = 0; i < n; i ++ ) cin >> a[i];
	reverse(a, a + n);
	reverse(a, a + m);
	reverse(a + m, a + n);
	for (int i = 0; i < n - 1; i ++ ) cout << a[i] << ' ';
	cout << a[n - 1];
	return 0;
}

用队列的版本：

#include <iostream>
#include <queue>
using namespace std;

int main(){
	int m, n;
	cin >> n >> m;
	m %= n;
	queue<int> q;
	for (int i = 0; i < n; i ++ ){
		int t;
		cin >> t;
		q.push(t);
	}
	if (m){
		for (int i = 0; i < n - m; i ++ ){
			int t = q.front();
			q.pop();
			q.push(t);
		}		
	}
	while (q.size() > 1){
		cout << q.front() << ' ';
		q.pop();
	}
	cout << q.front();
	return 0;
}

1009 说反话

温馨提示：循环输入按Ctrl+Z结束输入

#include <iostream>
#include <stack>
#include <string>
using namespace std;

int main(){
	stack<string> S;
	string t;
	while (cin >> t) S.push(t);
	while (S.size() > 1){
		cout << S.top() << ' ';
		S.pop();
	}
	cout << S.top();
	return 0;
}

1010 一元多项式求导

#include <iostream>
using namespace std;

int main(){
	int n, m;
	bool flag = false;
	while(cin >> n >> m){
		if (flag && m && n) cout << ' ';
		if (!m || !n) continue;
		else{
            cout << n * m << ' ' << m - 1;
		    flag = true;
        }
	}
	if (!flag) cout << "0 0";
	return 0;
}