LeetCode 200. 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

大致題意

找出島嶼的數量（1表示陸地）

題解

題目型別：dfs

我們遇到 1 便開始dfs消除關聯的陸地，並返回島嶼的大小，如果該島嶼有大小，證明其存在（消除之後算不存在），count + 1

程式碼如下

class Solution {
public:
    int numIslands(vector<vector<char>>& grid) {
        int count = 0;
        for (int i = 0; i < grid.size(); i++) {
            for (int j = 0; j < grid[i].size(); j++) {
                if (search(i, j, grid)) {
                    count ++;
                }
            }
        }
        return count;
    }
    int search(int row, int column, vector<vector<char>>& grid) {
        if (row >= 0 && column >= 0 && row < grid.size() && column < grid[row].size() && grid[row][column] == '1') {
            grid[row][column] = '0';
            return 1 + search(row + 1, column, grid) + search(row - 1, column, grid) + search(row, column + 1, grid) + search(row, column - 1, grid);
        }
        return 0;
    }
};