leetcode 733. Flood Fill 像素替换 + 十分典型的深度优先搜索DFS

柔光的暖阳◎ 2022-06-03 08:52 133阅读 0赞

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 \[0, 65535\].

本题题意很简单，直接做一个深度优先搜索DFS即可

代码如下：

#include <iostream>
    #include <vector>
    #include <map>
    #include <set>
    #include <queue>
    #include <stack>
    #include <string>
    #include <climits>
    #include <algorithm>
    #include <sstream>
    #include <functional>
    #include <bitset>
    #include <numeric>
    #include <cmath>
    #include <regex>
    
    using namespace std;
    
    
    
    class Solution 
    {
    public:
        vector<vector<int>> floodFill(vector<vector<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;
        }
    
        void dfs(vector<vector<int>>& a, int x, int y, int targetColor, int newColor)
        {
            int row = a.size(), col = a[0].size();
            if (x < 0 || x >= row || y < 0 || y >= col || a[x][y] != targetColor)
                return;
            else
            {
                a[x][y] = newColor;
                dfs(a, x - 1, y, targetColor, newColor);
                dfs(a, x + 1, y, targetColor, newColor);
                dfs(a, x, y - 1, targetColor, newColor);
                dfs(a, x, y + 1, targetColor, newColor);
            }
        }
    };