class Solution {
public:
int numIslands(vector<vector<char>>& grid) {
int res = 0;
for(int i=0;i<grid.size();i++)
{
for(int j=0;j<grid[0].size();j++)
{
if(grid[i][j] == '1')
{
dfs(grid, i, j);
res += 1;
}
}
}
return res;
}
void dfs(vector<vector<char>>& grid, int i, int j)
{
// edge
if(i<0 || i>= grid.size() || j<0 || j>= grid[0].size() || grid[i][j] != '1')
{
return;
}
grid[i][j] = '0';
dfs(grid, i+1, j);
dfs(grid, i-1, j);
dfs(grid, i, j+1);
dfs(grid, i, j-1);
}
};
Java Code：
public int numIslands(char[][] grid) {
if (grid == null || grid.length == 0 || grid[0].length == 0) return 0;
int count = 0;
for (int row = 0; row < grid.length; row++) {
for (int col = 0; col < grid[0].length; col++) {
if (grid[row][col] == '1') {
dfs(grid, row, col);
count++;
}
}
}
return count;
}
private void dfs(char[][] grid,int row,int col) {
if (row<0||row== grid.length||col<0||col==grid[0].length||grid[row][col]!='1') {
return;
}
grid[row][col] = '0';
dfs(grid, row-1, col);
dfs(grid, row+1, col);
dfs(grid, row, col+1);
dfs(grid, row, col-1);
}
Javascript Code:
/*
* @lc app=leetcode id=200 lang=javascript
*
* [200] Number of Islands
*/
function helper(grid, i, j, rows, cols) {
if (i < 0 || j < 0 || i > rows - 1 || j > cols - 1 || grid[i][j] === "0")
return;
grid[i][j] = "0";
helper(grid, i + 1, j, rows, cols);
helper(grid, i, j + 1, rows, cols);
helper(grid, i - 1, j, rows, cols);
helper(grid, i, j - 1, rows, cols);
}
/**
* @param {character[][]} grid
* @return {number}
*/
var numIslands = function (grid) {
let res = 0;
const rows = grid.length;
if (rows === 0) return 0;
const cols = grid[0].length;
for (let i = 0; i < rows; i++) {
for (let j = 0; j < cols; j++) {
if (grid[i][j] === "1") {
helper(grid, i, j, rows, cols);
res++;
}
}
}
return res;
};
python code:
class Solution:
def numIslands(self, grid: List[List[str]]) -> int:
if not grid: return 0
count = 0
for i in range(len(grid)):
for j in range(len(grid[0])):
if grid[i][j] == '1':
self.dfs(grid, i, j)
count += 1
return count
def dfs(self, grid, i, j):
if i < 0 or j < 0 or i >= len(grid) or j >= len(grid[0]) or grid[i][j] != '1':
return
grid[i][j] = '0'
self.dfs(grid, i + 1, j)
self.dfs(grid, i - 1, j)
self.dfs(grid, i, j + 1)
self.dfs(grid, i, j - 1)
