LeetCode 1254 Number of Closed Islands
题目分析
https://leetcode.com/problems/number-of-closed-islands/
与 LeetCode 200 Number of Islands 类似，只不过这次靠边的岛屿不算了。
深度优先搜索
真的离谱，200 号题目里 grid 是 char 数组，这里是 int 数组，看了半天才看出问题来。 除此之外，还有边界写错（忘记 -1），= 写成 ==。
class Solution {
public:
int closedIsland(vector<vector<int>>& grid) {
int count = 0;
for (int i=0; i<grid.size(); i++) {
for (int j=0; j<grid[0].size(); j++) {
if (grid[i][j] == 0) {
if (travelIsland(i, j, grid)) {
count++;
}
}
}
}
return count;
}
bool travelIsland(int i, int j, vector<vector<int>>& grid) {
if (i < 0 || j < 0 || i >= grid.size() || j >= grid[0].size()) return false;
if (grid[i][j] == 0) {
grid[i][j] = 2; // mark as visited island
bool f1 = travelIsland(i+1, j, grid);
bool f2 = travelIsland(i-1, j, grid);
bool f3 = travelIsland(i, j+1, grid);
bool f4 = travelIsland(i, j-1, grid);
return f1 && f2 && f3 && f4;
}
return true;
}
};