50 lines
1015 B
C++
50 lines
1015 B
C++
#include <bits/stdc++.h>
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using namespace std;
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const int N = 30;
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const int INF = 0x3f3f3f3f;
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int a[N];
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bool st[N];
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int n, k;
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int cnt;
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// vector<int> path;
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bool isPrime(int n) {
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if (n < 2) return false;
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for (int i = 2; i <= n / i; i++)
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if (n % i == 0) return false;
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return true;
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}
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void dfs(int step, int sum, int pre) {
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if (step == k + 1) {
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if (isPrime(sum)) {
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cnt++;
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// for (int i = 0; i < path.size(); i++) cout << path[i] << " ";
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// cout << endl;
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}
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return;
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}
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for (int i = pre + 1; i <= n; i++)
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if (!st[i]) {
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st[i] = true;
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// path.push_back(a[i]);
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dfs(step + 1, sum + a[i], i);
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// path.pop_back();
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st[i] = false;
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}
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}
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/*
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4 3
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3 7 12 19
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3+7+19=29
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答案：1
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*/
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int main() {
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cin >> n >> k;
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for (int i = 1; i <= n; i++) cin >> a[i];
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dfs(1, 0, 0);
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cout << cnt << endl;
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return 0;
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}
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