From b25eccbca5d52fd5a839e62ea08b64ad93dc3191 Mon Sep 17 00:00:00 2001
From: crupest <crupest@outlook.com>
Date: Sun, 28 Feb 2021 18:34:49 +0800
Subject: import(solutions): Add acwing 1209.

---
 works/solutions/acwing/1209.cpp | 48 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 works/solutions/acwing/1209.cpp

(limited to 'works')

diff --git a/works/solutions/acwing/1209.cpp b/works/solutions/acwing/1209.cpp
new file mode 100644
index 0000000..3f3ff7a
--- /dev/null
+++ b/works/solutions/acwing/1209.cpp
@@ -0,0 +1,48 @@
+#include <array>
+#include <iostream>
+#include <vector>
+
+int number;
+int count = 0;
+std::array<bool, 10> used{false};
+std::array<int, 9> current;
+
+int calc(int start, int end) {
+  int n = 0;
+  for (int i = start; i < end; i++) {
+    n *= 10;
+    n += current[i];
+  }
+  return n;
+}
+
+void dfs(int n) {
+  if (n == 9) {
+    for (int i = 1; i <= 7; i++)
+      for (int j = i + 1; j <= 8; j++) {
+        int a = calc(0, i);
+        int b = calc(i, j);
+        int c = calc(j, 9);
+        if ((number - a) * b == c) {
+          count++;
+        }
+      }
+    return;
+  }
+
+  for (int i = 1; i <= 9; i++) {
+    if (!used[i]) {
+      used[i] = true;
+      current[n] = i;
+      dfs(n + 1);
+      used[i] = false;
+    }
+  }
+}
+
+int main() {
+  std::cin >> number;
+  dfs(0);
+  std::cout << count;
+  return 0;
+}
-- 
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