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Number of Islands
Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.
Example 1:
11110 11010 11000 00000
Answer: 1
Example 2:
11000 11000 00100 00011
Answer: 3
Java代码：
public class Solution { public int numIslands(char[][] grid) { if (grid == null || grid.length == 0) { return 0; } int rowLen = grid.length; int colLen = grid[0].length; boolean[][] visited = new boolean[rowLen][colLen]; int[][] direct = new int[][]{ {-1, 0}, {1, 0}, {0, -1}, {0, 1}}; Deque queue = new ArrayDeque<>(); int res = 0; for (int i = 0; i < rowLen; i++) { for (int j = 0; j < colLen; j++) { if (!visited[i][j] && grid[i][j] == '1') { res++; queue.add(i * colLen + j); while (!queue.isEmpty()) { int pos = queue.poll(); int curr_x = pos / colLen; int curr_y = pos % colLen; if (visited[curr_x][curr_y]) { continue; } visited[curr_x][curr_y] = true; for (int k = 0; k < 4; k++) { int x = curr_x + direct[k][0]; int y = curr_y + direct[k][1]; if (x >= 0 && y >= 0 && x < rowLen && y < colLen && grid[x][y] == '1') { queue.add(x * colLen + y); } } } } } } return res; }} 转载地址：http://fvuni.baihongyu.com/