feat: implement LargestRectangleHistogram for calculating maximum rectangle area in a histogram

Author: sksahu01

src/main/java/com/thealgorithms/stacks/heights.java

@@ -0,0 +1,34 @@
+import java.util.Stack;
+
+public class LargestRectangleHistogram {
+    public static int largestRectangleArea(int[] heights) {
+        Stack<Integer> stack = new Stack<>();
+        int maxArea = 0;
+        int n = heights.length;
+
+        for (int i = 0; i <= n; i++) {
+            // Use 0 height at end to flush stack
+            int h = (i == n) ? 0 : heights[i];
+
+            while (!stack.isEmpty() && h < heights[stack.peek()]) {
+                int height = heights[stack.pop()];
+                int width;
+                if (stack.isEmpty()) {
+                    width = i; // rectangle extends from 0 to i-1
+                } else {
+                    width = i - stack.peek() - 1; // between previous smaller and i
+                }
+                maxArea = Math.max(maxArea, height * width);
+            }
+            stack.push(i);
+        }
+
+        return maxArea;
+    }
+
+    public static void main(String[] args) {
+        int[] heights = {2, 1, 5, 6, 2, 3};
+        int result = largestRectangleArea(heights);
+        System.out.println("Largest Rectangle Area: " + result);
+    }
+}