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Fix(searches): Correct column pointer initialization in RowColumnWiseSorted2dArrayBinarySearch #6333

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Merged
merged 3 commits into from
Jul 2, 2025
+128 −1
Merged

Fix(searches): Correct column pointer initialization in RowColumnWiseSorted2dArrayBinarySearch #6333

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6ca8592
Fix(searches): Correct column pointer initialization
codingmydna Jul 1, 2025
bae6cc9
Test: Add comprehensive tests for rectangular matrices
codingmydna Jul 2, 2025
0d4411a
Merge branch 'master' into fix/2d-array-search-bug
siriak Jul 2, 2025
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2 changes: 1 addition & 1 deletion src/main/java/com/thealgorithms/searches/RowColumnWiseSorted2dArrayBinarySearch.java
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Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,7 @@ public <T extends Comparable<T>> int[] find(T[][] matrix, T key) {

public static <T extends Comparable<T>> int[] search(T[][] matrix, T target) {
int rowPointer = 0; // The pointer at 0th row
int colPointer = matrix.length - 1; // The pointer at end column
int colPointer = matrix[0].length - 1; // The pointer at end column

while (rowPointer < matrix.length && colPointer >= 0) {
int comp = target.compareTo(matrix[rowPointer][colPointer]);
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127 changes: 127 additions & 0 deletions src/test/java/com/thealgorithms/searches/RowColumnWiseSorted2dArrayBinarySearchTest.java
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Expand Up @@ -110,4 +110,131 @@ public void rowColumnSorted2dArrayBinarySearchTestNotFound() {
assertEquals(expected[0], ans[0]);
assertEquals(expected[1], ans[1]);
}

/**
* Tests for a WIDE rectangular matrix (3 rows, 4 columns)
*/
private static final Integer[][] WIDE_RECTANGULAR_MATRIX = {
{10, 20, 30, 40},
{15, 25, 35, 45},
{18, 28, 38, 48},
};

@Test
public void rowColumnSorted2dArrayBinarySearchTestWideMatrixMiddle() {
Integer target = 25; // A value in the middle
int[] ans = RowColumnWiseSorted2dArrayBinarySearch.search(WIDE_RECTANGULAR_MATRIX, target);
int[] expected = {1, 1};
assertEquals(expected[0], ans[0]);
assertEquals(expected[1], ans[1]);
}

@Test
public void rowColumnSorted2dArrayBinarySearchTestWideMatrixTopRightCorner() {
Integer target = 40; // The top-right corner element
int[] ans = RowColumnWiseSorted2dArrayBinarySearch.search(WIDE_RECTANGULAR_MATRIX, target);
int[] expected = {0, 3};
assertEquals(expected[0], ans[0]);
assertEquals(expected[1], ans[1]);
}

@Test
public void rowColumnSorted2dArrayBinarySearchTestWideMatrixBottomLeftCorner() {
Integer target = 18; // The bottom-left corner element
int[] ans = RowColumnWiseSorted2dArrayBinarySearch.search(WIDE_RECTANGULAR_MATRIX, target);
int[] expected = {2, 0};
assertEquals(expected[0], ans[0]);
assertEquals(expected[1], ans[1]);
}

@Test
public void rowColumnSorted2dArrayBinarySearchTestWideMatrixTopLeftCorner() {
Integer target = 10; // The top-left corner element
int[] ans = RowColumnWiseSorted2dArrayBinarySearch.search(WIDE_RECTANGULAR_MATRIX, target);
int[] expected = {0, 0};
assertEquals(expected[0], ans[0]);
assertEquals(expected[1], ans[1]);
}

@Test
public void rowColumnSorted2dArrayBinarySearchTestWideMatrixBottomRightCorner() {
Integer target = 48; // The bottom-right corner element
int[] ans = RowColumnWiseSorted2dArrayBinarySearch.search(WIDE_RECTANGULAR_MATRIX, target);
int[] expected = {2, 3};
assertEquals(expected[0], ans[0]);
assertEquals(expected[1], ans[1]);
}

@Test
public void rowColumnSorted2dArrayBinarySearchTestWideMatrixNotFound() {
Integer target = 99; // A value that does not exist
int[] ans = RowColumnWiseSorted2dArrayBinarySearch.search(WIDE_RECTANGULAR_MATRIX, target);
int[] expected = {-1, -1};
assertEquals(expected[0], ans[0]);
assertEquals(expected[1], ans[1]);
}

/**
* Tests for a TALL rectangular matrix (4 rows, 3 columns)
*/
private static final Integer[][] TALL_RECTANGULAR_MATRIX = {
{10, 20, 30},
{15, 25, 35},
{18, 28, 38},
{21, 31, 41},
};

@Test
public void rowColumnSorted2dArrayBinarySearchTestTallMatrixMiddle() {
Integer target = 28; // A value in the middle
int[] ans = RowColumnWiseSorted2dArrayBinarySearch.search(TALL_RECTANGULAR_MATRIX, target);
int[] expected = {2, 1};
assertEquals(expected[0], ans[0]);
assertEquals(expected[1], ans[1]);
}

@Test
public void rowColumnSorted2dArrayBinarySearchTestTallMatrixTopRightCorner() {
Integer target = 30; // The top-right corner element
int[] ans = RowColumnWiseSorted2dArrayBinarySearch.search(TALL_RECTANGULAR_MATRIX, target);
int[] expected = {0, 2};
assertEquals(expected[0], ans[0]);
assertEquals(expected[1], ans[1]);
}

@Test
public void rowColumnSorted2dArrayBinarySearchTestTallMatrixBottomLeftCorner() {
Integer target = 21; // The bottom-left corner element
int[] ans = RowColumnWiseSorted2dArrayBinarySearch.search(TALL_RECTANGULAR_MATRIX, target);
int[] expected = {3, 0};
assertEquals(expected[0], ans[0]);
assertEquals(expected[1], ans[1]);
}

@Test
public void rowColumnSorted2dArrayBinarySearchTestTallMatrixTopLeftCorner() {
Integer target = 10; // The top-left corner element
int[] ans = RowColumnWiseSorted2dArrayBinarySearch.search(TALL_RECTANGULAR_MATRIX, target);
int[] expected = {0, 0};
assertEquals(expected[0], ans[0]);
assertEquals(expected[1], ans[1]);
}

@Test
public void rowColumnSorted2dArrayBinarySearchTestTallMatrixBottomRightCorner() {
Integer target = 41; // The bottom-right corner element
int[] ans = RowColumnWiseSorted2dArrayBinarySearch.search(TALL_RECTANGULAR_MATRIX, target);
int[] expected = {3, 2};
assertEquals(expected[0], ans[0]);
assertEquals(expected[1], ans[1]);
}

@Test
public void rowColumnSorted2dArrayBinarySearchTestTallMatrixNotFound() {
Integer target = 5; // A value that does not exist
int[] ans = RowColumnWiseSorted2dArrayBinarySearch.search(TALL_RECTANGULAR_MATRIX, target);
int[] expected = {-1, -1};
assertEquals(expected[0], ans[0]);
assertEquals(expected[1], ans[1]);
}
}
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