test: LargestRectangle (#5360)

Author: alxkm

src/test/java/com/thealgorithms/stacks/LargestRectangleTest.java

@@ -0,0 +1,77 @@
+package com.thealgorithms.stacks;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class LargestRectangleTest {
+
+    @Test
+    void testLargestRectangleHistogramWithTypicalCases() {
+        // Typical case with mixed heights
+        int[] heights = {2, 1, 5, 6, 2, 3};
+        String expected = "10";
+        String result = LargestRectangle.largestRectanglehistogram(heights);
+        assertEquals(expected, result);
+
+        // Another typical case with increasing heights
+        heights = new int[] {2, 4};
+        expected = "4";
+        result = LargestRectangle.largestRectanglehistogram(heights);
+        assertEquals(expected, result);
+
+        // Case with multiple bars of the same height
+        heights = new int[] {4, 4, 4, 4};
+        expected = "16";
+        result = LargestRectangle.largestRectanglehistogram(heights);
+        assertEquals(expected, result);
+    }
+
+    @Test
+    void testLargestRectangleHistogramWithEdgeCases() {
+        // Edge case with an empty array
+        int[] heights = {};
+        String expected = "0";
+        String result = LargestRectangle.largestRectanglehistogram(heights);
+        assertEquals(expected, result);
+
+        // Edge case with a single bar
+        heights = new int[] {5};
+        expected = "5";
+        result = LargestRectangle.largestRectanglehistogram(heights);
+        assertEquals(expected, result);
+
+        // Edge case with all bars of height 0
+        heights = new int[] {0, 0, 0};
+        expected = "0";
+        result = LargestRectangle.largestRectanglehistogram(heights);
+        assertEquals(expected, result);
+    }
+
+    @Test
+    void testLargestRectangleHistogramWithLargeInput() {
+        // Large input case
+        int[] heights = new int[10000];
+        for (int i = 0; i < heights.length; i++) {
+            heights[i] = 1;
+        }
+        String expected = "10000";
+        String result = LargestRectangle.largestRectanglehistogram(heights);
+        assertEquals(expected, result);
+    }
+
+    @Test
+    void testLargestRectangleHistogramWithComplexCases() {
+        // Complex case with a mix of heights
+        int[] heights = {6, 2, 5, 4, 5, 1, 6};
+        String expected = "12";
+        String result = LargestRectangle.largestRectanglehistogram(heights);
+        assertEquals(expected, result);
+
+        // Case with a peak in the middle
+        heights = new int[] {2, 1, 5, 6, 2, 3, 1};
+        expected = "10";
+        result = LargestRectangle.largestRectanglehistogram(heights);
+        assertEquals(expected, result);
+    }
+}