Narrow down common elements between strings

Question

public class numerodetel {**strong text**    
static void commun(String tel1, String tel2){
    for(int i=0;i<tel1.length();i++){
        for(int j=0;j<tel2.length();j++){
            if(tel1.charAt(i)==tel2.charAt(j))
                System.out.printf(" %c,", tel1.charAt(i));

        }

    }
}
public static void main(String[] args){
        String telUDM = "5143436111", telJean = "4501897654";

        commun(telUDM, telJean);
    }
}

The code works and I am able to find the common numbers between the two phone numbers. Is there an easy way, though, to make it so that once a common number is detected between the two, it doesn't reappear again? In this case it would be 5, 1, 4, 6.

Eduardo · Answer 1 · 2019-01-20T03:20:59.413

1

First you can remove the repeated numbers from the string using something like what is suggested here:

Removing duplicates from a String in Java

Then, you can use break statement to leave the inner loop every time a match is found:

static void commun(String tel1, String tel2) {
    for(int i=0;i<tel1.length();i++) {
        for(int j=0;j<tel2.length();j++) {
            if(tel1.charAt(i)==tel2.charAt(j)) {
                System.out.printf(" %c,", tel1.charAt(i));
                break;
            }
        }
    }
}

edited Jan 20 '19 at 03:20

answered Jan 20 '19 at 02:55

Eduardo

319
2
14

It still repeats numbers – Charles Allo Jan 20 '19 at 03:01
Are you sure? Does it keep going after "5" from "telUDM" and "45" from "4501897654"? – Eduardo Jan 20 '19 at 03:04
how would you do that – Charles Allo Jan 20 '19 at 03:04
when i only put break it still repeats – Charles Allo Jan 20 '19 at 03:04
but when i copy paste what you wrote it just stops at 5 and doesn't give anything else – Charles Allo Jan 20 '19 at 03:04
@CharlesAllo isn't that what you expected? To stop after you find a match? – Eduardo Jan 20 '19 at 03:10
yeah but I wanna find other matches so that it gives out: 5, 1, 4, 6 – Charles Allo Jan 20 '19 at 03:15
Ok. Now I got what you want. I guess the easiest way would be to remove the repeated numbers from the the first string and then to use this method. – Eduardo Jan 20 '19 at 03:17
Is there a method to systematically do that? Since these are phone numbers – Charles Allo Jan 20 '19 at 03:20
No, but you can write your own method if it will be useful for you multiple times. – Eduardo Jan 20 '19 at 03:22
Yeah the original question I'm asking how would one go about exactly that – Charles Allo Jan 20 '19 at 03:24

Til · Answer 2 · 2019-01-20T03:43:57.697

Try this:

public class numerodetel {**strong text**    
static void commun(String tel1, String tel2){
    dstr="";
    for(int i=0;i<tel1.length();i++){
        if (dstr.indexOf(tel1.charAt(i)) >= 0)
            continue;
        for(int j=0;j<tel2.length();j++){
            if (tel1.charAt(i)==tel2.charAt(j)) {
                dstr += tel1.charAt(i);
                System.out.printf(" %c,", tel1.charAt(i));
            }
        }

    }
}
public static void main(String[] args){
        String telUDM = "5143436111", telJean = "4501897654";

        commun(telUDM, telJean);
    }
}

Simply updated your own codes.
It's to maintain a dumplicates string dstr here, common chars will add into it.
When a letter already in it, then will skip the comparing by continue.
indexOf will return the position of the letter in the string, or -1 if not in it.

score 0 · Answer 3 · answered Jan 20 '19 at 03:38

If you don't want duplicates, use Set.

This will also perform better O(n+m), instead of the O(n*m) of your code.

static void commun(String tel1, String tel2) {
    Set<Integer> chars1 = tel1.chars().boxed().collect(Collectors.toSet());
    Set<Integer> chars2 = tel2.chars().boxed().collect(Collectors.toSet());
    chars1.retainAll(chars2);
    for (int ch : chars1)
        System.out.printf(" %c,", (char) ch);
}

Test

commun("5143436111", "4501897654");

Output

 1, 4, 5, 6,

Narrow down common elements between strings

3 Answers3