[Leetcode] 733. Flood Fill 解题报告

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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实现，该算法用于替换图像中特定区域的颜色。通过递归地访问图像中与起始像素颜色相同的所有相邻像素，并将它们的颜色替换为新的颜色，从而完成图像的修改。

题目：

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].

思路：

最最最原始的DFS题目^_^。

代码：

class Solution {
public:
    vector<vector<int>> floodFill(vector<vector<int>>& image, int sr, int sc, int newColor) {
        vector<vector<int>> new_image(image);
        int oldColor = image[sr][sc];
        if (oldColor != newColor) {
            DFS(new_image, sr, sc, oldColor, newColor);
        }
        return new_image;
    }
private:
    void DFS(vector<vector<int>> &new_image, int r, int c, int old_color, int new_color) {
        int row_num = new_image.size(), col_num = new_image[0].size();
        if (r < 0 || r >= row_num || c < 0 || c >= col_num || new_image[r][c] != old_color) {
            return;
        }
        new_image[r][c] = new_color;
        DFS(new_image, r - 1, c, old_color, new_color);
        DFS(new_image, r + 1, c, old_color, new_color);
        DFS(new_image, r, c - 1, old_color, new_color);
        DFS(new_image, r, c + 1, old_color, new_color);
    }
};