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NumberOfIslands
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NumberOfIslands
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// C++Program to count islands in boolean 2D matrix
#include <bits/stdc++.h>
using namespace std;
void DFS(vector<vector<int>> &M, int i, int j, int ROW,
int COL)
{
if (i < 0 || j < 0 || i > (ROW - 1) || j > (COL - 1) || M[i][j] != 1)
{
return;
}
if (M[i][j] == 1)
{
M[i][j] = 0;
DFS(M, i + 1, j, ROW, COL); //right side traversal
DFS(M, i - 1, j, ROW, COL); //left side traversal
DFS(M, i, j + 1, ROW, COL); //upward side traversal
DFS(M, i, j - 1, ROW, COL); //downward side traversal
DFS(M, i + 1, j + 1, ROW, COL); //upward-right side traversal
DFS(M, i - 1, j - 1, ROW, COL); //downward-left side traversal
DFS(M, i + 1, j - 1, ROW, COL); //downward-right side traversal
DFS(M, i - 1, j + 1, ROW, COL); //upward-left side traversal
}
}
int countIslands(vector<vector<int>> &M)
{
int ROW = M.size();
int COL = M[0].size();
int count = 0;
for (int i = 0; i < ROW; i++)
{
for (int j = 0; j < COL; j++)
{
if (M[i][j] == 1)
{
M[i][j] = 0;
count++;
DFS(M, i + 1, j, ROW, COL); //right side traversal
DFS(M, i - 1, j, ROW, COL); //left side traversal
DFS(M, i, j + 1, ROW, COL); //upward side traversal
DFS(M, i, j - 1, ROW, COL); //downward side traversal
DFS(M, i + 1, j + 1, ROW, COL); //upward-right side traversal
DFS(M, i - 1, j - 1, ROW, COL); //downward-left side traversal
DFS(M, i + 1, j - 1, ROW, COL); //downward-right side traversal
DFS(M, i - 1, j + 1, ROW, COL); //upward-left side traversal
}
}
}
return count;
}
// Driver Code
int main()
{
vector<vector<int>> M = {{1, 1, 0, 0, 0},
{0, 1, 0, 0, 1},
{1, 0, 0, 1, 1},
{0, 0, 0, 0, 0},
{1, 0, 1, 0, 1}};
cout << "Number of islands is: " << countIslands(M);
return 0;
}