'commit'

TangDou/Mkx/HDU2048_DFS.cpp

@@ -0,0 +1,37 @@
+#include <bits/stdc++.h>
+using namespace std;
+const int N = 110;
+typedef long long LL;
+// TLE　超时,看来，还是递推更安全些
+int n;
+LL res, sum;
+int st[N];
+void dfs(int u) {
+    if (u == n + 1) {
+        res++;
+        return;
+    }
+    for (int i = 1; i <= n; i++)
+        if (!st[i] && u != i) {
+            st[i] = true;
+            dfs(u + 1);
+            st[i] = false;
+        }
+}
+int main() {
+    int m;
+    scanf("%d", &m);
+
+    while (m--) {
+        scanf("%d", &n);
+        memset(st, 0, sizeof st);
+        sum = 1;
+        dfs(1);
+        //总次数
+        for (int i = 1; i <= n; i++) sum = sum * i;
+
+        //比率
+        printf("%.2lf%%\n", (double)res / sum * 100);
+    }
+    return 0;
+}