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Author: NinePiece2

Solutions/0733-flood-fill/README.md

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+<p>You are given an image represented by an <code>m x n</code> grid of integers <code>image</code>, where <code>image[i][j]</code> represents the pixel value of the image. You are also given three integers <code>sr</code>, <code>sc</code>, and <code>color</code>. Your task is to perform a <strong>flood fill</strong> on the image starting from the pixel <code>image[sr][sc]</code>.</p>
+
+<p>To perform a <strong>flood fill</strong>:</p>
+
+<ol>
+	<li>Begin with the starting pixel and change its color to <code>color</code>.</li>
+	<li>Perform the same process for each pixel that is <strong>directly adjacent</strong> (pixels that share a side with the original pixel, either horizontally or vertically) and shares the <strong>same color</strong> as the starting pixel.</li>
+	<li>Keep <strong>repeating</strong> this process by checking neighboring pixels of the <em>updated</em> pixels&nbsp;and modifying their color if it matches the original color of the starting pixel.</li>
+	<li>The process <strong>stops</strong> when there are <strong>no more</strong> adjacent pixels of the original color to update.</li>
+</ol>
+
+<p>Return the <strong>modified</strong> image after performing the flood fill.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">image = [[1,1,1],[1,1,0],[1,0,1]], sr = 1, sc = 1, color = 2</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">[[2,2,2],[2,2,0],[2,0,1]]</span></p>
+
+<p><strong>Explanation:</strong></p>
+
+<p><img alt="" src="https://assets.leetcode.com/uploads/2021/06/01/flood1-grid.jpg" style="width: 613px; height: 253px;" /></p>
+
+<p>From the center of the image with position <code>(sr, sc) = (1, 1)</code> (i.e., the red pixel), all pixels connected by a path of the same color as the starting pixel (i.e., the blue pixels) are colored with the new color.</p>
+
+<p>Note the bottom corner is <strong>not</strong> colored 2, because it is not horizontally or vertically connected to the starting pixel.</p>
+</div>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">image = [[0,0,0],[0,0,0]], sr = 0, sc = 0, color = 0</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">[[0,0,0],[0,0,0]]</span></p>
+
+<p><strong>Explanation:</strong></p>
+
+<p>The starting pixel is already colored with 0, which is the same as the target color. Therefore, no changes are made to the image.</p>
+</div>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>m == image.length</code></li>
+	<li><code>n == image[i].length</code></li>
+	<li><code>1 &lt;= m, n &lt;= 50</code></li>
+	<li><code>0 &lt;= image[i][j], color &lt; 2<sup>16</sup></code></li>
+	<li><code>0 &lt;= sr &lt; m</code></li>
+	<li><code>0 &lt;= sc &lt; n</code></li>
+</ul>

Solutions/0733-flood-fill/solution.py

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+class Solution:
+    def floodFill(self, image: List[List[int]], sr: int, sc: int, color: int) -> List[List[int]]:
+        directions = (-1, 0, 1, 0, -1)
+        original_colour = image[sr][sc]
+
+        def dfs(i: int, j: int):
+            image[i][j] = color
+            for val1, val2 in pairwise(directions):
+                x, y = i + val1, j + val2
+                if 0 <= x < len(image) and 0 <= y < len(image[0]) and image[x][y] == original_colour:
+                    dfs(x, y)
+        
+        if original_colour != color:
+            dfs(sr, sc)
+        return image