Added array problems

Author: Prashant Jain

.gitignore

@@ -26,3 +26,5 @@ hs_err_pid*
 *.iml
 build/
 out/
+.DS_Store
+

src/in/knowledgegate/dsa/array/SurfaceAreaOf3DShapes.java

@@ -0,0 +1,83 @@
+package in.knowledgegate.dsa.array;
+
+/**
+ * You are given an n x n grid where you have
+ * placed some 1 x 1 x 1 cubes. Each value v = grid[i][j]
+ * represents a tower of v cubes placed on top
+ * of cell (i, j).
+ *
+ * After placing these cubes, you have decided to
+ * glue any directly adjacent cubes to each other,
+ * forming several irregular 3D shapes.
+ *
+ * Return the total surface area of the resulting
+ * shapes.
+ *
+ * Note: The bottom face of each shape counts
+ * toward its surface area.
+ *
+ * Example 1:
+ * Input: grid = [[1,2],
+ *                [3,4]]
+ * Output: 34 = 4 + 7 + 10 + 13 = 34
+ *
+ * Example 2:
+ * Input: grid = [[1,1,1],
+ *                [1,0,1],
+ *                [1,1,1]]
+ * Output: 32
+ *
+ * Example 3:
+ * Input: grid = [[2,2,2],[2,1,2],[2,2,2]]
+ * Output: 46
+ *
+ * Constraints:
+ * n == grid.length == grid[i].length
+ * 1 <= n <= 50
+ * 0 <= grid[i][j] <= 50
+ */
+public class SurfaceAreaOf3DShapes {
+    public static void main(String[] args) {
+        SurfaceAreaOf3DShapes shapes =
+            new SurfaceAreaOf3DShapes();
+        int[][] grid = new int[][]{{1,2},{3,4}};
+        System.out.println("Area is:" + shapes.surfaceArea(grid));
+    }
+
+    public int surfaceArea(int[][] grid) {
+        int total = 0;
+        int size = grid.length;
+        for (int i = 0 ; i< size; i++) {
+            for (int j = 0; j < size; j++) {
+                if (grid[i][j] == 0) continue;
+                int areaGained =
+                    4 * grid[i][j] + 2;
+                int areaLost = 0;
+                if (i - 1 >= 0) {
+                    areaLost += Math.min(grid[i][j], grid[i-1][j]);
+                }
+                if (i + 1 < size) {
+                    areaLost += Math.min(grid[i][j], grid[i+1][j]);
+                }
+                if (j - 1 >= 0) {
+                    areaLost += Math.min(grid[i][j], grid[i][j-1]);
+                }
+                if (j + 1 < size) {
+                    areaLost += Math.min(grid[i][j], grid[i][j+1]);
+                }
+                total += areaGained - areaLost;
+            }
+        }
+
+        return total;
+    }
+}
+
+
+
+
+
+
+
+
+

src/in/knowledgegate/dsa/array/ValidSudoku.java

@@ -0,0 +1,95 @@
+package in.knowledgegate.dsa.array;
+
+import java.util.HashSet;
+import java.util.Set;
+
+/**
+ * Determine if a 9 x 9 Sudoku board is valid. Only
+ * the filled cells need to be validated according
+ * to the following rules:
+ *
+ * Each row must contain the digits 1-9 without repetition.
+ * Each column must contain the digits 1-9 without
+ * repetition.
+ * Each of the nine 3 x 3 sub-boxes of the grid must
+ * contain the digits 1-9 without repetition.
+ * Note:
+ *
+ * A Sudoku board (partially filled) could be valid
+ * but is not necessarily solvable.
+ * Only the filled cells need to be validated
+ * according to the mentioned rules.
+ *
+ *
+ * Example 1:
+ * Input: board =
+ * {   {'5','3','.','.','7','.','.','.','.'}
+ *   , {'6','.','.','1','9','5','.','.','.'}
+ *   , {'.','9','8','.','.','.','.','6','.'}
+ *   , {'8','.','.','.','6','.','.','.','3'}
+ *   , {'4','.','.','8','.','3','.','.','1'}
+ *   , {'7','.','.','.','2','.','.','.','6'}
+ *   , {'.','6','.','.','.','.','2','8','.'}
+ *   , {'.','.','.','4','1','9','.','.','5'}
+ *   , {'.','.','.','.','8','.','.','7','9'}}
+ * Output: true
+ *
+ * Example 2:
+ * Input: board =
+ * [["8","3",".",".","7",".",".",".","."]
+ * ,["6",".",".","1","9","5",".",".","."]
+ * ,[".","9","8",".",".",".",".","6","."]
+ * ,["8",".",".",".","6",".",".",".","3"]
+ * ,["4",".",".","8",".","3",".",".","1"]
+ * ,["7",".",".",".","2",".",".",".","6"]
+ * ,[".","6",".",".",".",".","2","8","."]
+ * ,[".",".",".","4","1","9",".",".","5"]
+ * ,[".",".",".",".","8",".",".","7","9"]]
+ * Output: false
+ *
+ * Explanation: Same as Example 1, except with the
+ * 5 in the top left corner being modified to 8.
+ * Since there are two 8's in the top left 3x3
+ * sub-box, it is invalid.
+ *
+ *
+ * Constraints:
+ * board.length == 9
+ * board[i].length == 9
+ * board[i][j] is a digit 1-9 or '.'.
+ */
+public class ValidSudoku {
+    public static void main(String[] args) {
+        ValidSudoku checker = new ValidSudoku();
+        char[][] puzzle = new char[][]
+            {{'5','3','.','.','7','.','.','.','.'}
+            ,{'6','.','.','1','9','5','.','.','.'}
+            ,{'.','9','8','.','.','.','.','6','.'}
+            ,{'8','.','.','.','6','.','.','.','3'}
+            ,{'4','.','.','8','.','3','.','.','1'}
+            ,{'7','.','.','.','2','.','.','.', '6'}
+            ,{'.','6','.','.','.','.','2','8','.'}
+            ,{'.','.','.','4','1','9','.','.','5'}
+            ,{'.','.','.','.','8','.','.', '7','9'}};
+        System.out.println("IsValid:" + checker.isValidSudoku(puzzle));
+    }
+
+    public boolean isValidSudoku(char[][] board) {
+        Set<String> visited = new HashSet<>();
+        for (int i = 0; i < 9; i++) {
+            for (int j = 0; j < 9; j++) {
+                char c = board[i][j];
+                if (c == '.') continue;
+                if (!visited.add(c +"row" + i) ||
+                !visited.add(c + "col" + j) ||
+                !visited.add(c + "box" + i/3 + "-" + j/3)) {
+                    return false;
+                }
+            }
+        }
+        return true;
+    }
+}
+
+
+