Sync LeetCode submission Runtime - 20 ms (73.28%), Memory - 65.6 MB (30.77%)

Author: koralkulacoglu

LeetCode/1507-check-if-there-is-a-valid-path-in-a-grid/README.md

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+<p>You are given an <code>m x n</code> <code>grid</code>. Each cell of <code>grid</code> represents a street. The street of <code>grid[i][j]</code> can be:</p>
+
+<ul>
+	<li><code>1</code> which means a street connecting the left cell and the right cell.</li>
+	<li><code>2</code> which means a street connecting the upper cell and the lower cell.</li>
+	<li><code>3</code> which means a street connecting the left cell and the lower cell.</li>
+	<li><code>4</code> which means a street connecting the right cell and the lower cell.</li>
+	<li><code>5</code> which means a street connecting the left cell and the upper cell.</li>
+	<li><code>6</code> which means a street connecting the right cell and the upper cell.</li>
+</ul>
+<img alt="" src="https://assets.leetcode.com/uploads/2020/03/05/main.png" style="width: 450px; height: 708px;" />
+<p>You will initially start at the street of the upper-left cell <code>(0, 0)</code>. A valid path in the grid is a path that starts from the upper left cell <code>(0, 0)</code> and ends at the bottom-right cell <code>(m - 1, n - 1)</code>. <strong>The path should only follow the streets</strong>.</p>
+
+<p><strong>Notice</strong> that you are <strong>not allowed</strong> to change any street.</p>
+
+<p>Return <code>true</code><em> if there is a valid path in the grid or </em><code>false</code><em> otherwise</em>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2020/03/05/e1.png" style="width: 455px; height: 311px;" />
+<pre>
+<strong>Input:</strong> grid = [[2,4,3],[6,5,2]]
+<strong>Output:</strong> true
+<strong>Explanation:</strong> As shown you can start at cell (0, 0) and visit all the cells of the grid to reach (m - 1, n - 1).
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2020/03/05/e2.png" style="width: 455px; height: 293px;" />
+<pre>
+<strong>Input:</strong> grid = [[1,2,1],[1,2,1]]
+<strong>Output:</strong> false
+<strong>Explanation:</strong> As shown you the street at cell (0, 0) is not connected with any street of any other cell and you will get stuck at cell (0, 0)
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> grid = [[1,1,2]]
+<strong>Output:</strong> false
+<strong>Explanation:</strong> You will get stuck at cell (0, 1) and you cannot reach cell (0, 2).
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>m == grid.length</code></li>
+	<li><code>n == grid[i].length</code></li>
+	<li><code>1 &lt;= m, n &lt;= 300</code></li>
+	<li><code>1 &lt;= grid[i][j] &lt;= 6</code></li>
+</ul>

LeetCode/1507-check-if-there-is-a-valid-path-in-a-grid/solution.cpp

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+class Solution {
+    vector<int> dx = {-1, 1, 0, 0};
+    vector<int> dy = {0, 0, -1, 1};
+    vector<vector<int>> vis;
+
+bool dfs(int x, int y, vector<vector<int>>& grid, vector<vector<bool>>& visited) {
+        int n = grid.size();
+        int m = grid[0].size();
+        
+        if (x == n - 1 && y == m - 1) return true;
+        
+        visited[x][y] = true;
+        int val = grid[x][y];
+
+        for (int i = 0; i < 4; i++) {
+            int nx = x + dx[i];
+            int ny = y + dy[i];
+
+            if (nx < 0 || nx >= n || ny < 0 || ny >= m || visited[nx][ny]) continue;
+            
+            int newVal = grid[nx][ny];
+
+            if (i == 0) {
+                if ((val == 2 || val == 5 || val == 6) && (newVal == 2 || newVal == 3 || newVal == 4)) {
+                    if (dfs(nx, ny, grid, visited)) return true;
+                }
+            }
+            else if (i == 1) {
+                if ((val == 2 || val == 3 || val == 4) && (newVal == 2 || newVal == 5 || newVal == 6)) {
+                    if (dfs(nx, ny, grid, visited)) return true;
+                }
+            }
+            else if (i == 2) {
+                if ((val == 1 || val == 3 || val == 5) && (newVal == 1 || newVal == 4 || newVal == 6)) {
+                    if (dfs(nx, ny, grid, visited)) return true;
+                }
+            }
+            else if (i == 3) {
+                if ((val == 1 || val == 4 || val == 6) && (newVal == 1 || newVal == 3 || newVal == 5)) {
+                    if (dfs(nx, ny, grid, visited)) return true;
+                }
+            }
+        }
+
+        return false;
+    }
+
+public:
+    bool hasValidPath(vector<vector<int>>& grid) {
+        int n = grid.size();
+        int m = grid[0].size();
+        vector<vector<bool>> visited(n, vector<bool>(m, false));
+        return dfs(0, 0, grid, visited);
+    }
+};