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103 lines
3.8 KiB
Java
103 lines
3.8 KiB
Java
package com.thealgorithms.others;
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import java.util.LinkedList;
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import java.util.Queue;
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/**
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* Implementation of the Flood Fill algorithm using an iterative BFS (Breadth-First Search) approach.
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*
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* <p>The Flood Fill algorithm is used to fill connected areas in an image with a new color, starting from a specified point.
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* This implementation uses an iterative BFS approach with a queue
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* instead of recursion to avoid stack overflow issues with large images.</p>
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*
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* <p><b>Implementation Features:</b></p>
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* <ul>
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* <li>Supports 8-connected filling (horizontal, vertical, and diagonal directions)</li>
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* <li>Uses BFS traversal through {@link java.util.Queue}</li>
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* <li>Includes nested {@code Point} class to represent pixel coordinates</li>
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* <li>Iterative approach avoids stack overflow for large images</li>
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* </ul>
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*
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* <p><b>Time Complexity:</b> O(M × N) where M and N are the dimensions of the image</p>
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* <p><b>Space Complexity:</b> O(M × N) in the worst case the queue stores every pixel</p>
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*
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* @see <a href="https://www.geeksforgeeks.org/dsa/flood-fill-algorithm">Flood Fill Algorithm - GeeksforGeeks</a>
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* @see <a href="https://en.wikipedia.org/wiki/Flood_fill">Flood Fill Algorithm - Wikipedia</a>
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*/
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public final class IterativeFloodFill {
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private IterativeFloodFill() {
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}
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/**
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* Iteratively fill the 2D image with new color
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*
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* @param image The image to be filled
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* @param x The x coordinate at which color is to be filled
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* @param y The y coordinate at which color is to be filled
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* @param newColor The new color which to be filled in the image
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* @param oldColor The old color which is to be replaced in the image
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* @see <a href=https://www.geeksforgeeks.org/dsa/flood-fill-algorithm>FloodFill BFS<a/>
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*/
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public static void floodFill(final int[][] image, final int x, final int y, final int newColor, final int oldColor) {
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if (image.length == 0 || image[0].length == 0 || newColor == oldColor || shouldSkipPixel(image, x, y, oldColor)) {
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return;
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}
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Queue<Point> queue = new LinkedList<>();
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queue.add(new Point(x, y));
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int[] dx = {0, 0, -1, 1, 1, -1, 1, -1};
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int[] dy = {-1, 1, 0, 0, -1, 1, 1, -1};
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while (!queue.isEmpty()) {
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Point currPoint = queue.poll();
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if (shouldSkipPixel(image, currPoint.x, currPoint.y, oldColor)) {
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continue;
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}
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image[currPoint.x][currPoint.y] = newColor;
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for (int i = 0; i < 8; i++) {
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int curX = currPoint.x + dx[i];
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int curY = currPoint.y + dy[i];
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if (!shouldSkipPixel(image, curX, curY, oldColor)) {
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queue.add(new Point(curX, curY));
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}
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}
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}
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}
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/**
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* Represents a point in 2D space with integer coordinates.
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*/
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private static class Point {
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final int x;
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final int y;
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Point(final int x, final int y) {
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this.x = x;
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this.y = y;
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}
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}
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/**
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* Checks if a pixel should be skipped during flood fill operation.
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*
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* @param image The image to get boundaries
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* @param x The x coordinate of pixel to check
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* @param y The y coordinate of pixel to check
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* @param oldColor The old color which is to be replaced in the image
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* @return {@code true} if pixel should be skipped, else {@code false}
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*/
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private static boolean shouldSkipPixel(final int[][] image, final int x, final int y, final int oldColor) {
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if (x < 0 || x >= image.length || y < 0 || y >= image[0].length || image[x][y] != oldColor) {
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return true;
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}
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return false;
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}
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}
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