733. Flood Fill

最新推荐文章于 2021-08-14 15:42:41 发布

BigFatSheep

最新推荐文章于 2021-08-14 15:42:41 发布

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分类专栏： Leetcode Easy

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本文介绍了一种基于深度优先搜索（DFS）的二维图像洪水填充算法。该算法用于替换从指定起点开始，所有与起点颜色相同的相邻像素的颜色。通过递归地访问与当前像素颜色相同的上下左右像素并更改其颜色，直到所有符合条件的像素都被覆盖。

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Description

An image is represented by a 2-D array of integers, each integer representing the pixel value of the image (from 0 to 65535).

Given a coordinate (sr, sc) representing the starting pixel (row and column) of the flood fill, and a pixel value newColor, “flood fill” the image.

To perform a “flood fill”, consider the starting pixel, plus any pixels connected 4-directionally to the starting pixel of the same color as the starting pixel, plus any pixels connected 4-directionally to those pixels (also with the same color as the starting pixel), and so on. Replace the color of all of the aforementioned pixels with the newColor.

At the end, return the modified image.

Example 1:
Input:
image = [[1,1,1],[1,1,0],[1,0,1]]
sr = 1, sc = 1, newColor = 2
Output: [[2,2,2],[2,2,0],[2,0,1]]
Explanation:
From the center of the image (with position (sr, sc) = (1, 1)), all pixels connected
by a path of the same color as the starting pixel are colored with the new color.
Note the bottom corner is not colored 2, because it is not 4-directionally connected
to the starting pixel.
Note:

The length of image and image[0] will be in the range [1, 50].
The given starting pixel will satisfy 0 <= sr < image.length and 0 <= sc < image[0].length.
The value of each color in image[i][j] and newColor will be an integer in [0, 65535].
Problem URL

Solution

给一个二维数组表示的image，给一个初始的点，将所有和这个点相连的相同颜色的点换为新的颜色。

Using DFS to solve this problem. Because it is simple. Judge newColor is same or not. Then start DFS, assign connected cell with same original color to new color.

Code

class Solution {
    public int[][] floodFill(int[][] image, int sr, int sc, int newColor) {
        if (image[sr][sc] == newColor){
            return image;
        }
        dfs(image, sr, sc, image[sr][sc], newColor);
        return image;
    }
    
    private void dfs(int[][] image, int sr, int sc, int color, int newColor){
        if (sr < 0 || sc < 0 || sr >= image.length || sc >= image[0].length || image[sr][sc] != color){
            return;
        }
        image[sr][sc] = newColor;
        dfs(image, sr + 1, sc, color, newColor);
        dfs(image, sr - 1, sc, color, newColor);
        dfs(image, sr, sc + 1, color, newColor);
        dfs(image, sr, sc - 1, color, newColor);
    }
        
}