版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/GYH0730/article/details/84338381
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:
Input: 11110 11010 11000 00000 Output: 1
Example 2:
Input: 11000 11000 00100 00011 Output: 3
题意：找出图中岛的个数。
思路：广搜
Java代码：
class node
{
int x,y;
node(int x,int y) {
this.x = x;
this.y = y;
}
}
public class Solution {
public void BFS(int sx,int sy,char[][] grid)
{
int[][] to = new int[][]{ {1,0},{-1,0},{0,1},{0,-1} };
node[] queue = new node[20005];
int head,tail;
head = tail = 0;
grid[sx][sy] = '-';
queue[tail++] = new node(sx,sy);
while(head < tail) {
node now = queue[head++];
int tx,ty;
for(int i = 0; i < 4; i++) {
tx = now.x + to[i][0];
ty = now.y + to[i][1];
if( !(tx >= 0 && ty >= 0 && tx < grid.length && ty < grid[0].length) ) continue;
if(grid[tx][ty] != '1') continue;
grid[tx][ty] = '-';
queue[tail++] = new node(tx,ty);
}
}
}
public int numIslands(char[][] grid) {
int num = 0;
for(int i = 0; i < grid.length; i++) {
for(int j = 0; j < grid[i].length; j++) {
if(grid[i][j] == '1') {
num++;
BFS(i,j,grid);
}
}
}
return num;
}
}