[leetcode] 1591. strange-printer-ii.cpp

Author: cycheng

README.md

@@ -99,6 +99,7 @@
 #### [Biweekly 35](https://leetcode.com/contest/biweekly-contest-35/ranking)
   * (5) [1589. maximum-sum-obtained-of-any-permutation.cpp](https://github.com/cycheng/coding-for-fun/blob/master/leetcode/1589.%20maximum-sum-obtained-of-any-permutation.cpp)
   * (5) [1590. make-sum-divisible-by-p.cpp](https://github.com/cycheng/coding-for-fun/blob/master/leetcode/1590.%20make-sum-divisible-by-p.cpp)
+  * (6) [1591. strange-printer-ii.cpp](https://github.com/cycheng/coding-for-fun/blob/master/leetcode/1591.%20strange-printer-ii.cpp)
 
 #### [2019 Facebook Hacker Cup](https://www.facebook.com/codingcompetitions/hacker-cup/2019)
   * [Qualification Round](https://www.facebook.com/codingcompetitions/hacker-cup/2019/qualification-round)

leetcode/1591. strange-printer-ii.cpp

@@ -0,0 +1,63 @@
+// https://leetcode.com/contest/biweekly-contest-35/problems/strange-printer-ii/
+//
+// #biweekly 35
+// #6, #topological order, #greedy, #like
+
+// Given a [m x n] matrix, the grid value means color.
+//
+// Each turn, we can print a solid rectangular of a color in the matrix.
+// The same color cannot be used again.
+//
+// Given a [m x n] matrix targetGrid, return true if it doesn't volatile the
+// above rule, else return false.
+#include "std.h"
+
+enum {
+  UNINIT,
+  VISITED,
+  CHECKED,
+};
+bool dfsHasLoop(const unordered_set<int> edges[61], vector<int> &state,
+                int color) {
+  state[color] = VISITED;
+  for (int v : edges[color]) {
+    if (state[v] == CHECKED)
+      continue;
+    if (state[v] == VISITED)
+      return true;
+    if (dfsHasLoop(edges, state, v))
+      return true;
+  }
+  state[color] = CHECKED;
+  return false;
+}
+
+bool isPrintable(vector<vector<int>> &targetGrid) {
+  const int m = targetGrid.size(), n = targetGrid[0].size();
+  unordered_set<int> edges[61];
+  // greedy, O(CMN)
+  for (int color = 1; color <= 60; ++color) {
+    int top = m, left = n, right = 0, bottom = 0;
+    for (int i = 0; i < m; ++i)
+      for (int j = 0; j < n; ++j)
+        if (color == targetGrid[i][j]) {
+          top = min(top, i);
+          left = min(left, j);
+          right = max(right, j);
+          bottom = max(bottom, i);
+        }
+
+    // find overlapped grid
+    for (int i = top; i <= bottom; ++i)
+      for (int j = left; j <= right; ++j)
+        if (color != targetGrid[i][j])
+          edges[color].insert(targetGrid[i][j]);
+  }
+
+  // dfs check loop
+  vector<int> state(61);
+  for (int color = 1; color <= 60; ++color)
+    if (dfsHasLoop(edges, state, color))
+      return false;
+  return true;
+}