Add lambda solve

Author: colorbox

695/step2_3.cpp

@@ -0,0 +1,67 @@
+/*
+Time : O()
+Space : O(N * M)
+
+ラムダを用いてstackへの要素追加部分のロジックを修正したものt
+*/
+class Solution {
+ public:
+  int maxAreaOfIsland(vector<vector<int>>& grid) {
+    const int row_count = grid.size();
+    const int col_count = grid.front().size();
+    auto visited = vector<vector<char>>(row_count, vector<char>(col_count, '0'));
+    int max_island_area = 0;
+    for (int row = 0; row < row_count; ++row) {
+      for (int col = 0; col < col_count; ++col) {
+        if (grid[row][col] == kSea) {
+          continue;
+        }
+        const int area = CountIslandArea(row, col, row_count, col_count, grid, visited);
+        max_island_area = max(max_island_area, area);
+      }
+    }
+    return max_island_area;
+  }
+
+ private:
+  static constexpr int kSea = 0;
+
+  int CountIslandArea(const int row, const int col,
+                      const int row_count, const int col_count,
+                      const vector<vector<int>>& grid,
+                      vector<vector<char>>&visited) {
+    stack<pair<int, int>> next_coordinates;
+    next_coordinates.emplace(row, col);
+    int area = 0;
+
+    auto emplace_if_countable = [&grid, &visited, &next_coordinates, row_count, col_count](
+        const int row,
+        const int col)  {
+      if (!(0 <= row && row < row_count && 0 <= col && col < col_count)) {
+        return;
+      }
+      if (grid[row][col] == kSea) {
+        return;
+      }
+      if (visited[row][col] == '1') {
+        return;
+      }
+      next_coordinates.emplace(row, col);
+    };
+
+    while (!next_coordinates.empty()) {
+      auto [row, col] = next_coordinates.top();
+      next_coordinates.pop();
+      if (visited[row][col] == '1') {
+        continue;
+      }
+      visited[row][col] = '1';
+      ++area;
+      emplace_if_countable(row + 1, col);
+      emplace_if_countable(row - 1, col);
+      emplace_if_countable(row, col + 1);
+      emplace_if_countable(row, col - 1);
+    }
+    return area;
+  }
+};