HISTOGRAM (giving wrong answer for all test cases)

#1

import java.util.*;
public class Main {

public static void main(String[] args) throws Exception {
	// TODO Auto-generated method stub
	Scanner s = new Scanner(System.in);
	
	int n = s.nextInt();
	int[] arr = new int[n];
	
	for(int i = 0;i < n;i++)
	    arr[i] = s.nextInt();
	    
		Main mainobj = new Main();
		StacksUsingArrays stack = mainobj.new StacksUsingArrays(1000);
		System.out.println(hist(arr, stack));
	}


public static long hist(int[] arr, StacksUsingArrays stack) throws Exception {

	int max_area = 0; 
	int tp; 
	int area_with_top; 

	int i = 0;
	while (i < arr.length) {

		if (stack.isEmpty() || arr[stack.top()] <= arr[i])
			stack.push(i++);

		else {
			tp = stack.top();
			stack.pop();

			area_with_top = arr[tp] * (stack.isEmpty() ? i : i - stack.top() - 1);

			if (max_area < area_with_top)
				max_area = area_with_top;
		}
	}

	while (stack.isEmpty() == false) {
		tp = stack.top();
		stack.pop();
		area_with_top = arr[tp] * (stack.isEmpty() ? i : i - stack.top() - 1);

		if (max_area < area_with_top)
			max_area = area_with_top;
	}

	return max_area;
    
}

private class StacksUsingArrays {
	private int[] data;
	private int tos;

	public static final int DEFAULT_CAPACITY = 10;

	public StacksUsingArrays() throws Exception {
		// TODO Auto-generated constructor stub
		this(DEFAULT_CAPACITY);
	}

	public StacksUsingArrays(int capacity) throws Exception {
		if (capacity <= 0) {
			System.out.println("Invalid Capacity");
		}
		this.data = new int[capacity];
		this.tos = -1;
	}

	public int size() {
		return this.tos + 1;
	}

	public boolean isEmpty() {
		if (this.size() == 0) {
			return true;
		} else {
			return false;
		}
	}

	public void push(int item) throws Exception {
		if (this.size() == this.data.length) {
			throw new Exception("Stack is Full");
		}
		this.tos++;
		this.data[this.tos] = item;
	}

	public int pop() throws Exception {
		if (this.size() == 0) {
			throw new Exception("Stack is Empty");
		}
		int retVal = this.data[this.tos];
		this.data[this.tos] = 0;
		this.tos--;
		return retVal;
	}

	public int top() throws Exception {
		if (this.size() == 0) {
			throw new Exception("Stack is Empty");
		}
		int retVal = this.data[this.tos];
		return retVal;
	}

	public void display() throws Exception {
		if (this.size() == 0) {
			throw new Exception("Stack is Empty");
		}
		for (int i = this.tos; i >= 0; i--) {
			System.out.println(this.data[i]);
		}

	}

}

}

#2

@10vaibhavsinghnegi take into consideration the long constraints which are failing your code

#3

i have changed returning value to long but it’s not working…do i need to change something else?

#4 
public static long hist(int[] arr, StacksUsingArrays stack) throws Exception {

long max_area = 0; //long
int tp; 
long area_with_top; //long

int i = 0;
while (i < arr.length) {

	if (stack.isEmpty() || arr[stack.top()] <= arr[i])
		stack.push(i++);

	else {
		tp = stack.top();
		stack.pop();

		area_with_top = arr[tp] * (stack.isEmpty() ? i : i - stack.top() - 1);

		if (max_area < area_with_top)
			max_area = area_with_top;
	}
}

while (stack.isEmpty() == false) {
	tp = stack.top();
	stack.pop();
	area_with_top = arr[tp] * (stack.isEmpty() ? i : i - stack.top() - 1);

	if (max_area < area_with_top)
		max_area = area_with_top;
}

return max_area;

}