Create 1020-number-of-enclaves.java

Author: Anukriti167

java/1020-number-of-enclaves.java

@@ -0,0 +1,46 @@
+/*
+The basic idea is to iterate through the boundary
+If we encounter any island i.e. 1 then we will run DFS
+And update all those islands as 2
+
+Then check for the number of 1s remaining in the board 
+Since those are the ones that have not been visited and return
+*/
+
+class Solution {
+    public int count(int [][]board){
+        int c = 0;
+        for(int i=0; i<board.length; i++){
+            for(int j=0; j<board[0].length; j++){
+                if(board[i][j] == 1){
+                    c++;
+                }
+            }
+        }
+        return c;
+    }
+    public void dfs(int r, int c, int[][] board){
+        if(r<0 || c<0 || r>board.length-1 || c>board[0].length-1 || board[r][c] != 1) return;
+
+        board[r][c] = 2;
+
+        dfs(r+1, c, board);
+        dfs(r-1, c, board);
+        dfs(r, c+1, board);
+        dfs(r, c-1, board);
+    }
+    public int numEnclaves(int[][] board) {
+        int n=board.length, m=board[0].length;
+
+        for(int i=0; i<n; i++){
+            if(board[i][0] == 1) dfs(i, 0, board);
+            if(board[i][m-1] == 1) dfs(i, m-1, board);
+        }
+
+        for(int i=1; i<m-1; i++){
+            if(board[0][i] == 1) dfs(0, i, board);
+            if(board[n-1][i] == 1) dfs(n-1, i, board);
+        }
+        return count(board);
+    }
+}