Flood Fill
<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://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0700-0799/0733.Flood%20Fill/images/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>
Depth-First Search; Breadth-First Search; Array; Matrix
class Solution {
    private int[][] image;
    private int oc;
    private int color;
    private final int[] dirs = {-1, 0, 1, 0, -1};

    public int[][] floodFill(int[][] image, int sr, int sc, int color) {
        oc = image[sr][sc];
        if (oc == color) {
            return image;
        }
        this.image = image;
        this.color = color;
        dfs(sr, sc);
        return image;
    }

    private void dfs(int i, int j) {
        image[i][j] = color;
        for (int k = 0; k < 4; ++k) {
            int x = i + dirs[k], y = j + dirs[k + 1];
            if (x >= 0 && x < image.length && y >= 0 && y < image[0].length && image[x][y] == oc) {
                dfs(x, y);
            }
        }
    }
}
