Largest Rectangle in Histogram

LargestRectangle.java

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+import java.util.Stack;
+
+public class LargestRectangle {
+    public static void main(String[] args) {
+        int[] arr = {2,1,5,6,2,3};
+
+        int res = largestRectangleArea(arr);
+            System.out.println(res);
+
+
+    }
+    public static int largestRectangleArea(int[] heights) {
+        int len = heights.length;
+        Stack<Integer> s = new Stack<>();
+        int maxArea = 0;
+        for (int i = 0; i <= len; i++){
+            int h = (i == len ? 0 : heights[i]);
+            if (s.isEmpty() || h >= heights[s.peek()]) {
+                s.push(i);
+            } else {
+                int top = s.pop();
+                maxArea = Math.max(maxArea, heights[top] * (s.isEmpty() ? i : i - 1 - s.peek()));
+                i--;
+            }
+        }
+        return maxArea;
+    }
+}
+
+
+