[60pts] #1224. [常中20180905 T1] 今天你AK了吗？

https://sjzezoj.com/submission/47985

S2OJ/1224/1224.cpp

@@ -0,0 +1,49 @@
+#include <cmath>
+#include <iostream>
+#include <vector>
+
+using std::cin;
+using std::cout;
+using std::endl;
+
+const int N = 100005;
+
+int n;
+long long k, permutation[N];
+bool vis[N];
+
+inline long long fact(long long x) {
+    long long res = 1;
+    while (x) {
+        res *= x--;
+    }
+    return res;
+}
+
+void revContor(int n, long long k) {
+    k--;
+    for (int i = 1; i <= n; i++) {
+        long long cnt = k / fact(n - i);
+        for (int j = 1; j <= n; j++) {
+            if (!vis[j]) {
+                if (!cnt) {
+                    permutation[i] = j;
+                    vis[j] = true;
+                    break;
+                }
+                cnt--;
+            }
+        }
+        k %= fact(n - i);
+    }
+}
+
+int main() {
+    cin >> n >> k;
+    revContor(n, k);
+    for (int i = 1; i <= n; i++) {
+        cout << permutation[i] << ' ';
+    }
+    cout << endl;
+    return 0;
+}