695. Max Area of Island
1. Description
Given a non-empty 2D array grid of 0’s and 1’s, an island is a group of 1’s (representing land) connected 4-directionally (horizontal or vertical.) You may assume all four edges of the grid are surrounded by water.
Find the maximum area of an island in the given 2D array. (If there is no island, the maximum area is 0.)
2. Example
Example 1:
[[0,0,1,0,0,0,0,1,0,0,0,0,0],
[0,0,0,0,0,0,0,1,1,1,0,0,0],
[0,1,1,0,1,0,0,0,0,0,0,0,0],
[0,1,0,0,1,1,0,0,1,0,1,0,0],
[0,1,0,0,1,1,0,0,1,1,1,0,0],
[0,0,0,0,0,0,0,0,0,0,1,0,0],
[0,0,0,0,0,0,0,1,1,1,0,0,0],
[0,0,0,0,0,0,0,1,1,0,0,0,0]]
Given the above grid, return 6. Note the answer is not 11, because the island must be connected 4-directionally.
Example 2:
[[0,0,0,0,0,0,0,0]]
Given the above grid, return 0.
3. Note
- The length of each dimension in the given grid does not exceed 50.
4. Solutions
My Accepted Solution
n is the number of elements in m_grid
Time complexity: O(n)
Space complexity: O(n)
class Solution {
public:
// int maxAreaOfIsland(vector<vector<int>>& grid)
int maxAreaOfIsland(vector<vector<int>>& m_grid) {
const int rows = m_grid.size(), columns = m_grid[0].size();
int maxArea = 0;
for (int i = 0; i < rows; ++i) {
for (int j = 0; j < columns; ++j) {
int area = searchIsland(m_grid, i, j);
maxArea = max(area, maxArea);
}
}
return maxArea;
}
private:
int searchIsland(vector<vector<int>>& m_grid, int row, int column) {
int area = 0;
searchIsland(m_grid, row, column, area);
return area;
}
void searchIsland(vector<vector<int>>& m_grid, int row, int column, int& m_area) {
if (0 <= row && row < m_grid.size() && 0 <= column && column < m_grid[0].size()) {
if (m_grid[row][column] == 1) {
++m_area;
m_grid[row][column] = 0;
searchIsland(m_grid, row + 1, column, m_area);
searchIsland(m_grid, row - 1, column, m_area);
searchIsland(m_grid, row, column + 1, m_area);
searchIsland(m_grid, row, column - 1, m_area);
}
}
}
};