Search2DMatrix.java

Author: MohakAgrawal25

src/main/java/com/thealgorithms/matrix/Search2DMatrix.java

@@ -2,86 +2,82 @@
 
 /**
  * Two variations of searching in a 2D matrix
- * 
+ *
  * Variation 1:
  * - Each row is sorted left to right
  * - Each column is sorted top to bottom
- * 
+ *
  * Variation 2:
  * - The matrix is a flattened sorted array
  * - i.e., row 0 ends, row 1 continues (matrix is sorted as a 1D array)
- * 
+ *
  * LeetCode: #74 and #240
  */
 public class Search2DMatrix {
 
     /**
-     * Variation 1: Search in a matrix where each row and each column is sorted
-     * Time: O(m + n)
+     * Search in a 2D matrix where rows and columns are sorted.
      *
-     * @param matrix input matrix
-     * @param target value to find
-     * @return true if found, false otherwise
+     * @param matrix The 2D matrix with sorted rows and columns.
+     * @param target The target integer to search for.
+     * @return true if target is found, otherwise false.
      */
     public static boolean searchMatrixSortedRowsAndCols(int[][] matrix, int target) {
-        int rows = matrix.length;
-        if (rows == 0) return false;
+        if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
+            return false;
+        }
 
+        int rows = matrix.length;
         int cols = matrix[0].length;
-        int row = 0, col = cols - 1;
+
+        int row = 0;
+        int col = cols - 1;
 
         while (row < rows && col >= 0) {
             int val = matrix[row][col];
-            if (val == target) return true;
-            else if (val > target) col--;
-            else row++;
+            if (val == target) {
+                return true;
+            } else if (val > target) {
+                col--;
+            } else {
+                row++;
+            }
         }
 
         return false;
     }
 
     /**
-     * Variation 2: Search in a matrix that behaves like a flattened sorted array
-     * Time: O(log(m * n))
+     * Search in a 2D matrix that is sorted as if flattened into a 1D array.
      *
-     * @param matrix input matrix
-     * @param target value to find
-     * @return true if found, false otherwise
+     * @param matrix The 2D matrix.
+     * @param target The target integer to search for.
+     * @return true if target is found, otherwise false.
      */
     public static boolean searchMatrixFlattenedSorted(int[][] matrix, int target) {
-        int rows = matrix.length;
-        if (rows == 0) return false;
+        if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
+            return false;
+        }
 
+        int rows = matrix.length;
         int cols = matrix[0].length;
-        int left = 0, right = rows * cols - 1;
+
+        int left = 0;
+        int right = rows * cols - 1;
 
         while (left <= right) {
             int mid = left + (right - left) / 2;
             int val = matrix[mid / cols][mid % cols];
 
-            if (val == target) return true;
-            else if (val < target) left = mid + 1;
-            else right = mid - 1;
+            if (val == target) {
+                return true;
+            } else if (val < target) {
+                left = mid + 1;
+            } else {
+                right = mid - 1;
+            }
         }
 
         return false;
     }
-
-    // Example usage
-    public static void main(String[] args) {
-        int[][] matrix1 = {
-            {1, 4, 7, 11},
-            {2, 5, 8, 12},
-            {3, 6, 9, 16},
-            {10, 13, 14, 17}
-        };
-        System.out.println(searchMatrixSortedRowsAndCols(matrix1, 5));  // true
-
-        int[][] matrix2 = {
-            {1, 3, 5, 7},
-            {10, 11, 16, 20},
-            {23, 30, 34, 50}
-        };
-        System.out.println(searchMatrixFlattenedSorted(matrix2, 3));   // true
-    }
 }