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
Solution 1: max CC question in graph, use DFS.
public class Solution {
public int numIslands(char[][] grid) {
int m=grid.length;
if (m==0) return 0;
int n=grid[0].length;
int count=0;
for (int i=0; i<m; i++) {
for (int j=0; j<n; j++) {
if (grid[i][j]=='1') {
count++;
dfs(grid,i,j,m,n);
}
}
}
return count;
}
private void dfs(char[][] grid, int i, int j, int m, int n) {
if (i<0 || i>=m) return;
if (j<0 || j>=n) return;
if (grid[i][j]!='1') return;
grid[i][j]='x';
dfs(grid,i+1,j,m,n);
dfs(grid,i-1,j,m,n);
dfs(grid,i,j+1,m,n);
dfs(grid,i,j-1,m,n);
}
}
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