fix(searches): fix out-of-bounds in single-row and single-column in BinarySearch2dArray

Author: hardikkaurani

src/main/java/com/thealgorithms/searches/BinarySearch2dArray.java

@@ -28,13 +28,13 @@ private BinarySearch2dArray() {
      * @return An array containing the row and column indices of the target, or [-1,
      *         -1] if the target is not found.
      */
-    static int[] binarySearch(int[][] arr, int target) {
+    public static int[] binarySearch(int[][] arr, int target) {
         int rowCount = arr.length;
         int colCount = arr[0].length;
 
         // Edge case: If there's only one row, search that row directly.
         if (rowCount == 1) {
-            return binarySearch(arr, target, 0, 0, colCount);
+            return binarySearch(arr, target, 0, 0, colCount - 1);
         }
 
         // Set initial boundaries for binary search on rows.
@@ -70,6 +70,11 @@ else if (arr[midRow][midCol] < target) {
             return new int[] {endRow, midCol};
         }
 
+        // Edge case: If there is only one column, target cannot be outside midCol.
+        if (colCount == 1) {
+            return new int[] {-1, -1};
+        }
+
         // If target is smaller than the element in the left of startRow, perform a
         // binary search on the left of startRow.
         if (target <= arr[startRow][midCol - 1]) {

src/test/java/com/thealgorithms/searches/BinarySearch2dArrayTest.java

@@ -1,5 +1,6 @@
 package com.thealgorithms.searches;
 
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
@@ -84,7 +85,7 @@ public void binarySearch2dArrayTestLowerSide() {
     // valid test case
     public void binarySearch2dArrayTestNotFound() {
         int[][] arr = {{1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10, 11, 12}};
-        int target = 101;
+        int target = 100;
 
         int[] ans = BinarySearch2dArray.binarySearch(arr, target);
         System.out.println(Arrays.toString(ans));
@@ -93,7 +94,7 @@ public void binarySearch2dArrayTestNotFound() {
     }
 
     /**
-     * Test if the method works with input arrays consisting only of one row.
+     * Test if the method works with an array that only has one row.
      */
     @Test
     public void binarySearch2dArrayTestOneRow() {
@@ -154,4 +155,52 @@ public void binarySearch2dArrayTestEmptyArray() {
         // Assert that an empty array is not valid input for the method.
         assertThrows(ArrayIndexOutOfBoundsException.class, () -> BinarySearch2dArray.binarySearch(arr, target));
     }
+
+    @Test
+    public void binarySearch2dArrayTestSingleRowTargetNotFoundGreater() {
+        int[][] arr = {{1, 2, 3, 4}};
+        int target = 10;
+        int[] ans = BinarySearch2dArray.binarySearch(arr, target);
+        assertArrayEquals(new int[] {-1, -1}, ans);
+    }
+
+    @Test
+    public void binarySearch2dArrayTestSingleRowTargetNotFoundSmaller() {
+        int[][] arr = {{1, 2, 3, 4}};
+        int target = 0;
+        int[] ans = BinarySearch2dArray.binarySearch(arr, target);
+        assertArrayEquals(new int[] {-1, -1}, ans);
+    }
+
+    @Test
+    public void binarySearch2dArrayTestSingleColumnPresent() {
+        int[][] arr = {{1}, {3}, {5}};
+        int target = 3;
+        int[] ans = BinarySearch2dArray.binarySearch(arr, target);
+        assertArrayEquals(new int[] {1, 0}, ans);
+    }
+
+    @Test
+    public void binarySearch2dArrayTestSingleColumnNotFound() {
+        int[][] arr = {{1}, {3}, {5}};
+        int target = 4;
+        int[] ans = BinarySearch2dArray.binarySearch(arr, target);
+        assertArrayEquals(new int[] {-1, -1}, ans);
+    }
+
+    @Test
+    public void binarySearch2dArrayTestSingleElementPresent() {
+        int[][] arr = {{42}};
+        int target = 42;
+        int[] ans = BinarySearch2dArray.binarySearch(arr, target);
+        assertArrayEquals(new int[] {0, 0}, ans);
+    }
+
+    @Test
+    public void binarySearch2dArrayTestSingleElementNotFound() {
+        int[][] arr = {{42}};
+        int target = 10;
+        int[] ans = BinarySearch2dArray.binarySearch(arr, target);
+        assertArrayEquals(new int[] {-1, -1}, ans);
+    }
 }