NextGreaterElement.java

import java.util.Arrays;

/**
1. transverse from RHS & select min
2. Swap with peak+1(we've started from RH) element
3. sort the rest number 
 */
public class NextGreaterElement 
{
public static void main(String[] args) 
{
    
}
static int nextGreaterElement(int n) 
{
char[] number = (n + "").toCharArray();
//1
int i, j;
for (i = number.length-1; i > 0; i--)
    if (number[i-1] < number[i])
       break;
// If no such digit is found, its the edge case 1.
if (i == 0)
    return -1;
    
 // II) Find the smallest digit on right side of (i-1)'th 
 // digit that is greater than number[i-1]
int x = number[i-1], smallest = i;
for (j = i+1; j < number.length; j++)
    if (number[j] > x && number[j] <= number[smallest])
        smallest = j;

// III) Swap the above found smallest digit with 
// number[i-1]
char temp = number[i-1];
number[i-1] = number[smallest];
number[smallest] = temp;

// IV) Sort the digits after (i-1) in ascending order
Arrays.sort(number, i, number.length);

long val = Long.parseLong(new String(number));
return (val <= Integer.MAX_VALUE) ? (int) val : -1;    
}
}