9.flood-fill.js

// // https://leetcode.com/problems/flood-fill/

// An image is represented by an m x n integer grid image where image[i][j] represents the pixel value of the image.
// You are also given three integers sr, sc, and color. You should perform a flood fill on the image starting from the pixel image[sr][sc].
// 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),
// and so on. Replace the color of all of the aforementioned pixels with color.
// Return the modified image after performing the flood fill.

// Example 1:
// Input: image = [[1,1,1],[1,1,0],[1,0,1]], sr = 1, sc = 1, color = 2
// Output: [[2,2,2],[2,2,0],[2,0,1]]
// Explanation: From the center of the image with position (sr, sc) = (1, 1) (i.e., the red pixel), all pixels connected by a path of the same color as the starting pixel (i.e., the blue pixels) 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.
// Example 2:
// Input: image = [[0,0,0],[0,0,0]], sr = 0, sc = 0, color = 0
// Output: [[0,0,0],[0,0,0]]
// Explanation: The starting pixel is already colored 0, so no changes are made to the image.

// Constraints:
// m == image.length
// n == image[i].length
// 1 <= m, n <= 50
// 0 <= image[i][j], color < 216
// 0 <= sr < m
// 0 <= sc < n

/**
 * @param {number[][]} image
 * @param {number} sr
 * @param {number} sc
 * @param {number} color
 * @return {number[][]}
 */
var floodFill = function (image, sr, sc, newColor) {

    if (image == null || image.length < 1 || image[sr][sc] === newColor) {
        return image
    }

    const height = image.length;
    const width = image[0].length;

    var fill = (r, c, oldColor, newColor) => {
        if (r < 0 || c < 0 || r > height - 1 || c > width - 1) {
            return
        }
        if (image[r][c] === newColor || image[r][c] !== oldColor) {
            return
        }

        image[r][c] = newColor;

        fill(r + 1, c, oldColor, newColor)
        fill(r - 1, c, oldColor, newColor)
        fill(r, c + 1, oldColor, newColor)
        fill(r, c - 1, oldColor, newColor)
    }

    fill(sr, sc, image[sr][sc], newColor)
    return image
};