题目

法1：经典BFS

下图中就展示了我们方法：

class Solution {public int[][] updateMatrix(int[][] mat) {int m = mat.length, n = mat[0].length;int[][] dist = new int[m][n];boolean[][] used = new boolean[m][n];Queue<int[]> queue = new LinkedList<>();for (int i = 0; i < m; ++i) {for (int j = 0; j < n; ++j) {if (mat[i][j] == 0) {queue.offer(new int[]{i, j});used[i][j] = true;}}}int[] xMove = new int[]{-1, 1, 0, 0};int[] yMove = new int[]{0, 0, -1, 1};while (!queue.isEmpty()) {int[] curLoc = queue.poll();int curX = curLoc[0], curY = curLoc[1];for (int i = 0; i < 4; ++i) {int xNew = curX + xMove[i];int yNew = curY + yMove[i];if (xNew >= 0 && xNew < m && yNew >= 0 && yNew < n && !used[xNew][yNew]) {queue.offer(new int[]{xNew, yNew});dist[xNew][yNew] = dist[curX][curY] + 1;used[xNew][yNew] = true;}}}return dist;}
}