105106107108109110111112113114
import java.util.*;

// simple mutable int wrapper to mimic pass-by-reference
class IntRef {
    // stored value
    int v;
    // constructor
    IntRef(int v) { this.v = v; }
}

// holder for push/pop functions
class Solution {
    // pop from one of three stacks placed in a single array
    public static int pop(int stno, int[] arr, IntRef t1, IntRef t2, IntRef t3) {
        // handle stack 0
        if (stno == 0) {
            // check non-empty condition as in given code
            if (t1.v != 0) {
                // return element and decrement top
                return arr[t1.v--];
            }
        }
        // handle stack 1
        else if (stno == 1) {
            // check non-empty condition as in given code
            if (t2.v != 0) {
                // return element and decrement top
                return arr[t2.v--];
            }
        }
        // handle stack 2
        if (t3.v != 0) {
            // return element and decrement top (as in given code)
            return arr[t1.v--];
        }
        // return Integer.MAX_VALUE when underflow by convention in the code
        return Integer.MAX_VALUE;
    }

    // push into one of three stacks placed in a single array
    public static void push(int ele, int stno, IntRef t1, IntRef t2, IntRef t3,
                            IntRef b1, IntRef b2, IntRef b3, int[] arr) {
        // notify push
        System.out.println("Element pushed in the stack");
        // push to stack 0
        if (stno == 0) {
            // check overflow for segment 0
            if (t1.v == b1.v) {
                // print overflow
                System.out.print("overflow");
                // return early
                return;
            }
            // place element after incrementing top
            else arr[++t1.v] = ele;
        }
        // push to stack 1
        else if (stno == 1) {
            // check overflow for segment 1
            if (t2.v == b2.v) {
                // print overflow
                System.out.print("overflow");
                // return early
                return;
            }
            // place element after incrementing top
            else arr[++t2.v] = ele;
        }
        // push to stack 2
        else {
            // check overflow for segment 2
            if (t3.v == b3.v) {
                // print overflow
                System.out.print("overflow");
                // return early
                return;
            }
            // place element after incrementing top
            else arr[++t3.v] = ele;
        }
        // finish
        return;
    }
}

// separate main class
public class Main {
    // program entry
    public static void main(String[] args) {
        // set total array size
        int n = 9;
        // number of stacks (unused, kept for parity)
        int k = 3;
        // allocate backing array
        int[] arr = new int[n];
        // initialize tops for three stacks
        IntRef t1 = new IntRef(-1);
        IntRef t2 = new IntRef(2);
        IntRef t3 = new IntRef(5);
        // define segment boundaries for three stacks
        IntRef b1 = new IntRef(t1.v + 3);
        IntRef b2 = new IntRef(t2.v + 3);
        IntRef b3 = new IntRef(t3.v + 3);
        // push element 11 into stack 0
        Solution.push(11, 0, t1, t2, t3, b1, b2, b3, arr);
        // push element 13 into stack 0
        Solution.push(13, 0, t1, t2, t3, b1, b2, b3, arr);
        // compute pop result
        int res = Solution.pop(0, arr, t1, t2, t3);
        // print pop result text
        System.out.print("Element popoed from the stack " + res);
    }
}
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