Question

Write a method called is1to1 that accepts a map whose keys and values are strings as its parameter and returns true if no two keys map to the same value. For example, {Marty=206– 9024, Hawking=123–4567, Smith=949–0504, Newton=123–4567} should return false, but {Marty=206–9024, Hawking=555–1234, Smith=949–0504, Newton=123–4567} should return true. The empty map is considered 1-to-1 and returns true.

Answer 1

import java.util.*;

class Main{

    static boolean is1to1(Map<String,String> map){
        //Set to store values
        Set<String> set = new HashSet<>();
        //Iterate through all keys in map
        for(String s : map.keySet()){
            //If value is present in the set , return false
            if(set.contains(map.get(s))){
                return false;
            }
            //Add value to set
            set.add(map.get(s));
        }
        return true;
    }
    public static void main(String[] args) {
        Map<String,String> map = new HashMap<>();
        map.put("Marty","206-9024");
        map.put("Hawking","123-4567");
        map.put("Smith","949-0504");
        map.put("Newton","123-4567");
        System.out.println(map+" is1to1() = "+is1to1(map));

        Map<String,String> map2 = new HashMap<>();
        map2.put("Marty","206-9024");
        map2.put("Hawking","555-1234");
        map2.put("Smith","949-0504");
        map2.put("Newton","123-4567");
        System.out.println(map2+" is1to1() = "+is1to1(map2));
    }
}