Algo-Trian

Algorithm/Graph/DFS/P1036 [NOIP 2002 普及组] 选数.cpp

@@ -0,0 +1,39 @@
+#include <iostream>
+#include <vector>
+using namespace std;
+
+int js = 0;
+vector<int> arr;
+
+bool checkprime(int x) {
+    if (x < 2) return false;
+    for (int i = 2; i * i <= x; i++) {
+        if (x % i == 0) return false;
+    }
+    return true;
+}
+
+void dfs(int idx, int k, int sum) {
+    if (k == 0) { // <20>Ѿ<EFBFBD>ѡ<EFBFBD><D1A1>k<EFBFBD><6B>
+        if (checkprime(sum)) js++;
+        return;
+    }
+    if (idx >= arr.size()) return;
+
+    // ѡ<><D1A1><EFBFBD><EFBFBD>ǰ<EFBFBD><C7B0>
+    dfs(idx + 1, k - 1, sum + arr[idx]);
+    // <20><>ѡ<EFBFBD><D1A1>ǰ<EFBFBD><C7B0>
+    dfs(idx + 1, k, sum);
+}
+
+int main() {
+    int n, k;
+    cin >> n >> k;
+    arr.resize(n);
+    for (int i = 0; i < n; i++) cin >> arr[i];
+
+    dfs(0, k, 0);
+    cout << js << endl;
+    return 0;
+}
+