Pairsum2.java

import java.util.ArrayList;

public class Pairsum2 {
    public static boolean pairsum(ArrayList<Integer> list, int  target){
        int bp = -1;
        int n = list.size();
        for (int i = 0; i < list.size(); i++){
            if(list.get(i) > list.get(i+1)){ // breaking point
                bp = i;
                break;
            }  
        }
        int lp =  bp + 1; //smallest
        int rp = bp;    // largest
        while(lp != rp){
            //case 1
           if(list.get(lp) + list.get(rp) == target){
            return true;
           } 
           //case 2
            if(list.get(lp) + list.get(rp)<target){
             lp = (lp+1) % n;
           }
           //case 3
           else {
             rp = (n+rp-1) % n;
           }
        }
        return false;
    }
    public static void main(String[] args) {
        ArrayList<Integer> list = new ArrayList<>();
        list.add(11);
        list.add(15);
        list.add(6);
        list.add(8);
        list.add(10);
        int target = 16;
        
        System.out.println(pairsum(list, target));

    }
}