AddingTwoSetOfIntervals.java

package com.interview.misc;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class AddingTwoSetOfIntervals {

    public static class Pair implements Comparable<Pair>{
        int low;
        int high;
        Pair(int low,int high){
            this.low = low;
            this.high = high;
        }
        @Override
        public int compareTo(Pair o) {
            if(this.low <= o.low){
                return -1;
            }else{
                return 1;
            }
        }
        
        public String toString(){
            return low + " " + high;
        }
    }
    
    public List<Pair> combineInterval(Pair[] arr1, Pair[] arr2){
        Arrays.sort(arr1);
        Arrays.sort(arr2);
        
        List<Pair> result = new ArrayList<Pair>();
        int i=0;
        int j=0;
        Pair current = new Pair(Integer.MIN_VALUE,Integer.MIN_VALUE+1);
        while(i < arr1.length && j < arr2.length){
            if(arr1[i].low <= arr2[j].low){
                if(arr1[i].low <= current.high){
                    current.high = Math.max(arr1[i].high,current.high);
                }else{
                    current = arr1[i];
                    result.add(current);
                }
                i++;
            }
            else{
                if(arr2[j].low <= current.high){
                    current.high = Math.max(arr2[j].high,current.high);
                }else{
                    current = arr2[j];
                    result.add(current);
                }
                j++;
            }
        }
        while(i < arr1.length){
            if(arr1[i].low <= current.high){
                current.high = Math.max(current.high,arr1[i].high);
            }else{
                current = arr1[i];
                result.add(current);
            }
            i++;
        }
        while(j < arr2.length){
            if(arr2[j].low <= current.high){
                current.high = Math.max(current.high, arr2[j].high);
            }else{
                current = arr2[j];
                result.add(current);
            }
            j++;
        }
        
        return result;
    }
    
    public static void main(String args[]){
        Pair p1 = new Pair(1,3);
        Pair p2 = new Pair(4,6);
        Pair p3 = new Pair(9,15);
        Pair p4 = new Pair(14,18);
        
        Pair[] arr1 = {p1,p2,p3,p4};
        
        Pair r1 = new Pair(2,4);
        Pair r2 = new Pair(7,8);
        Pair r3 = new Pair(11,13);
        
        Pair[] arr2 = {r1,r2,r3};
        
        AddingTwoSetOfIntervals ats = new AddingTwoSetOfIntervals();
        List<Pair> rs = ats.combineInterval(arr1, arr2);
        System.out.print(rs);
    }
    
}