May LeetCoding Challenge11 之 floodfill

1.DFS

2.BFS

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

class Solution {
    public int[][] floodFill(int[][] image, int sr, int sc, int newColor) {
        int m = image.length;
        int n = image[0].length;
        int[] dx = {-1, 1, 0, 0};//搜寻附近坐标
        int[] dy = {0, 0, -1, 1};
        int t = n*sr + sc; //坐标换算，二维变一维
        Deque<Integer> queue = new ArrayDeque<>();
        Set<Integer> visited = new HashSet<>();
        int preColor = image[sr][sc];
        image[sr][sc] = newColor;
        queue.addLast(t);
        visited.add(t);//记录是否遍历过
        while(!queue.isEmpty()){
            int loc = queue.removeFirst();
            int y = loc % n;
            int x = loc / n;
            for(int i = 0; i < dx.length; i++){
                int nx = x+dx[i];
                int ny = y+dy[i];
                int nc = nx*n + ny;
                if(nx >= 0 && nx < m && ny >= 0 && ny < n && preColor == image[nx][ny] && !visited.contains(nc)){
                    image[nx][ny] = newColor;
                    queue.addLast(nc);
                    visited.add(nc);
                }
            }          
        }
        return image;
    }
}

Python3

class Solution:
    def floodFill(self, image: List[List[int]], sr: int, sc: int, newColor: int) -> List[List[int]]:
        row = len(image)
        col = len(image[0])
        precolor = image[sr][sc];
        if precolor == newColor: return image
        def dfs(r, c):
            if image[r][c] == precolor:
                image[r][c] = newColor;
                if r-1 >= 0: dfs(r-1, c)
                if r+1 < row: dfs(r+1, c)
                if c-1 >= 0: dfs(r, c-1)
                if c+1 < col: dfs(r, c+1)
        dfs(sr, sc)
        return image

class Solution:
    def floodFill(self, image: List[List[int]], sr: int, sc: int, newColor: int) -> List[List[int]]:
        row = len(image)
        col = len(image[0])
        queue = []
        visited = set()
        precolor = image[sr][sc]
        if precolor == newColor: return image
        image[sr][sc] = newColor
        queue.append((sr, sc))
        visited.add((sr, sc))
        while queue:
            x, y = queue.pop(0)
            for i, j in [(x-1, y), (x+1, y), (x, y-1), (x, y+1)]:
                if 0<=i<row and 0<=j<col and image[i][j]==precolor and (i, j) not in visited:
                    image[i][j] = newColor
                    queue.append((i,j))
                    visited.add((i,j))
        return image