leetcode problem

Author: C5141506

src/main/problems/java_problem/backtracking/Palindrom.java

@@ -0,0 +1,58 @@
+package java_problem.backtracking;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+
+
+public class Palindrom {
+    // Online Java Compiler
+// Use this editor to write, compile and run your Java code online
+    public static void main(String[] args) {
+        HashSet<List<String>> res = new HashSet<List<String>>();
+        SolutionPalindrome solutionPalindrome=new SolutionPalindrome();
+        String s = "cdd";
+        solutionPalindrome.partition(s, res);
+        System.out.println(res);
+    }
+
+
+}
+class SolutionPalindrome {
+
+    public List<List<String>> partition(String s,HashSet<List<String>> res) {
+        int n = s.length();
+        if(n==0) return new ArrayList<List<String>>();
+        partition(s, 0, new ArrayList<String>(),res);
+        return new ArrayList(res);
+    }
+
+    public void partition(String s, int start, List<String> ls,HashSet<List<String>> res) {
+
+        if (start == s.length())  {
+            res.add(new ArrayList<String>(ls));
+        };
+
+        for (int end = start; end < s.length(); end++) {
+            if(isPalindrome(s, start, end)) {
+                ls.add(s.substring(start, end+1));
+                partition(s, end+1, ls,res);
+                ls.remove(ls.size()-1);
+            }
+        }
+
+    }
+
+    public boolean isPalindrome(String s, int start, int end) {
+        while (start < end) {
+            if (s.charAt(start) != s.charAt(end)) {
+                return false;
+            }
+            start++;
+            end--;
+        }
+        return true;
+    }
+}
+
+

src/main/problems/java_problem/graph/SurroundedRegion.java

@@ -0,0 +1,86 @@
+package java_problem.graph;
+
+public class SurroundedRegion {
+    public static void main(String[] args) {
+        char[][] board =
+                {{'X', 'X', 'X', 'X'}, {'X', 'O', 'O', 'X'}, {'X', 'X', 'O', 'X'}, {'X', 'O', 'X', 'X'}};
+        Solution solution = new Solution();
+        solution.solve(board);
+    }
+}
+
+class Solution {
+    public void solve(char[][] board) {
+        int rowNo = board.length;
+        int colNo = board[0].length;
+
+        visitBoundary(board, rowNo, colNo);
+        flip(board, rowNo, colNo);
+
+    }
+
+    public void flip(char[][] board, int row, int col) {
+        for (int i = 0; i < row; i++) {
+            for (int j = 0; j < col; j++) {
+                if (board[i][j] == 'O')
+                    board[i][j] = 'X';
+
+            }
+        }
+    }
+
+    public void visitBoundary(char[][] board, int rowNo, int colNo) {
+        //visit top row to check O
+        for (int col = 0; col < colNo; col++) {
+            if (board[0][col] == 'O') {
+                board[0][col] = 'V';
+                dfs(0, col, board);
+            }
+        }
+
+        //visit bottom row to check O
+        for (int col = 0; col < colNo; col++) {
+            if (board[rowNo - 1][col] == 'O') {
+                board[rowNo - 1][col] = 'V';
+                dfs(rowNo, col, board);
+            }
+        }
+
+        //visit left column to check O
+        for (int row = 0; row < rowNo; row++) {
+            if (board[row][0] == 'O') {
+                board[row][0] = 'V';
+                dfs(row, 0, board);
+            }
+        }
+
+        //visit right column to check O
+        for (int row = 0; row < rowNo; row++) {
+            if (board[colNo - 1][row] == 'O') {
+                board[colNo - 1][row] = 'V';
+                dfs(colNo - 1, row, board);
+            }
+        }
+    }
+
+    public void dfs(int row, int col, char[][] grid) {
+        if (row < 0 || row >= grid.length || col < 0 || col >= grid[0].length || grid[row][col] == 'V') {
+            return;
+        }
+
+        //mark as visited cell
+        if (grid[row][col] == 'O')
+            grid[row][col] = 'V';
+
+        dfs(row - 1, col, grid);
+        dfs(row, col - 1, grid);
+        dfs(row, col + 1, grid);
+        dfs(row + 1, col, grid);
+    }
+
+}
+
+
+
+
+