/**

* Given an array, find the next greater element G[i] for

* every element A[i] in the array.

* The Next greater Element for an element A[i] is the first

* greater element on the right side of A[i] in array.

*/

import java.util.*;

// Doing this as I need to have the index of the pushed item from the given array

class item {

int index;

Integer value;

item(int i, Integer v){index = i; value = v;}

}

public class Solution {

public ArrayList<Integer> nextGreater(ArrayList<Integer> a) {

int i,s;

Integer element,next;

item I,It;

Stack st = new Stack();

s = a.size();

ArrayList<Integer> result = a;

I = new item(0,new Integer(a.get(0)));

st.push(I);

for(i=1; i < s; i++){

next = a.get(i);

if(!st.empty()){

It = (item) st.pop();

element = It.value;

while(element < next){

result.set(It.index,next);

if(st.empty()) break;

It = (item) st.pop();

element = It.value;

}

if(element >= next){

st.push(It);

}

}

I = new item(i,next);

st.push(I);

}

while(!st.empty()){

It = (item) st.pop();

element = It.value;

result.set(It.index, new Integer(-1));

}

return result;

}

}