ABC357C Sierpinsky Carpet

atcoder/abc357c_sierpinski_carpet.cpp

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+// Vicfred
+// https://atcoder.jp/contests/abc357/tasks/abc357_c
+// implementation, recursion
+#include <cmath>
+#include <iostream>
+
+using namespace std;
+
+int n;
+char grid[1000][1000];
+
+void dfs(int n, int x, int y) {
+  if (n == 0) {
+    grid[x][y] = '#';
+    return;
+  }
+  dfs(n - 1, x, y);
+  dfs(n - 1, x, y + pow(3, n - 1));
+  dfs(n - 1, x, y + pow(3, n - 1) * 2);
+  dfs(n - 1, x + pow(3, n - 1), y);
+  dfs(n - 1, x + pow(3, n - 1), y + pow(3, n - 1) * 2);
+  dfs(n - 1, x + pow(3, n - 1) * 2, y);
+  dfs(n - 1, x + pow(3, n - 1) * 2, y + pow(3, n - 1));
+  dfs(n - 1, x + pow(3, n - 1) * 2, y + pow(3, n - 1) * 2);
+  for (int i = 0; i < pow(3, n - 1); ++i) {
+    for (int j = 0; j < pow(3, n - 1); ++j) {
+      grid[x + (int)pow(3, n - 1) + i][y + (int)pow(3, n - 1) + j] = '.';
+    }
+  }
+}
+
+int main() {
+  cin >> n;
+  dfs(n, 1, 1);
+  for (int i = 1; i <= pow(3, n); ++i) {
+    for (int j = 1; j <= pow(3, n); ++j) {
+      cout << grid[i][j];
+    }
+    cout << endl;
+  }
+  return 0;
+}