733. Flood Fill

QUESTION:

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.lengthand 0 <= sc < image[0].length.

The value of each color in image[i][j] and newColor will be an integer in [0, 65535].

EXPLANATION:

这个就是典型的泛洪算法，分为4方向和8方向的。

可以采用递归的方式进行：

将目标点的前后左右都进行，看看是否是oldcolor，如果是，那么就进入下一个循环，如果不是那么就不需要了。

SOLUTION:

class Solution {
    public int[][] floodFill(int[][] image, int sr, int sc, int newColor) {
        if(image[sr][sc]==newColor) return image;
        floodFillHelper(image,sr,sc,image[sr][sc],newColor);
        return image;
    }
    public static void floodFillHelper(int[][] image,int sr,int sc,int oldColor, int newColor){
        image[sr][sc] = newColor;
        if(sr>0 && image[sr-1][sc]==oldColor) floodFillHelper(image,sr-1,sc,oldColor,newColor);
        if(sc>0 && image[sr][sc-1]==oldColor) floodFillHelper(image,sr,sc-1,oldColor,newColor);
        if(sr<image.length-1 && image[sr+1][sc]==oldColor) floodFillHelper(image,sr+1,sc,oldColor,newColor);
        if(sc<image[0].length-1 && image[sr][sc+1]==oldColor) floodFillHelper(image,sr,sc+1,oldColor,newColor);
    }
}
--> return <--