USACO1.5.3 SuperPrime Rib (sprime)

dfs水题。先枚举个位，再枚举十位，依次类推。

/*ID:shijiey1PROG:sprimeLANG:C++*/#include <cstdio>#include <cstring>#include <algorithm>#include <queue>#include <vector>#include <cmath>using namespace std;int n;priority_queue<int, vector<int>, greater<int> > q;bool isPrime(int a) {if (a == 1 || !a) return false;bool flag = false;for (int i = 2; i <= sqrt(a); i++) {if (!(a % i)) {flag = true;break;}}return !flag;}void dfs(int step, int cur) {if (step == n) {q.push(cur);return;}int t;for (int i = 1; i <= 9; i++) {t = cur * 10 + i;if (isPrime(t)) {dfs(step + 1, t);}}}int main() {freopen("sprime.in", "r", stdin);freopen("sprime.out", "w", stdout);scanf("%d", &n);dfs(0, 0);while (!q.empty()) {printf("%d\n", q.top());q.pop();}return 0;}