How to find the index of an element in an array?

Question

I'm trying to solve this question:

String[] names = {
"Elena", "Thomas", "Hamilton", "Suzie", "Phil", "Matt", "Alex",
"Emma", "John", "James", "Jane", "Emily", "Daniel", "Neda",
"Aaron", "Kate"
};

int[] times = {
341, 273, 278, 329, 445, 402, 388, 275, 243, 334, 412, 393, 299,
343, 317, 265
};

basically there are 2 arrays, one for the names and one for the times, array indexes are matching (for example Elena's time is 341), I have to find the fastest runner, so whoever has the smallest time is the fastest.

first I found the smallest value in times array.

for (int i = 0; i < array.length; i++) {
    if(times[i] < fastest)
        fastest = times[i];
}

but I don't know how to match names array with times array, I tried this but it didn't work

System.out.println(Arrays.asList(names).indexOf(fastest));

Why not just keep track of the index and use that when you loop? — DeeV
– DeeV, Commented Dec 7, 2016 at 19:12
tried putting System.out.println(names[i]); in for loop, in this case the last output would be the fastest but I just want only 1 output — Ege Kuzubasioglu
– Ege Kuzubasioglu, Commented Dec 7, 2016 at 19:16

RAZ_Muh_Taz · Accepted Answer · 2016-12-07 20:06:59Z

4

How about:

public class test {


public static void main(String[] args)
{

    String[] names = {
            "Elena", "Thomas", "Hamilton", "Suzie", "Phil", "Matt", "Alex",
            "Emma", "John", "James", "Jane", "Emily", "Daniel", "Neda",
            "Aaron", "Kate"
            };

            int[] times = {
            341, 273, 278, 329, 445, 402, 388, 275, 243, 334, 412, 393, 299,
            343, 317, 265
            };

            int fastest = Integer.MAX_VALUE;
    int slowestRunnner = 0;

            for (int i = 0; i < times.length; i++) {
                if(times[i] < fastest)
                {
                    fastest = times[i];
                    slowestRunnner = i;
                }
            }

            System.out.println(names[slowestRunnner]);
}
}

System.out.println(names[slowestRunner]);

edited Dec 7, 2016 at 20:06

RAZ_Muh_Taz

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answered Dec 7, 2016 at 19:16

java_doctor_101

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10 Comments

Ege Kuzubasioglu Over a year ago

thanks for the answer, it worked, I did int slowestRunnner first, I didn't set it to zero and got an error, can you explain why I should set it to any integer in advance?

RAZ_Muh_Taz Over a year ago

maybe i am just having a brain fart but the above code will always give you i = array.length -1 becuase you don't have brackets around the if statement therefore only fastest = times[i] will execute for the if and slowestRunner = i gets set every iteration of the loop...?

java_doctor_101 Over a year ago

A local variable must be explicitly given a value before it is used, by either initialization or assignment, in a way that can be verified by the compiler using the rules for definite assignment.

java_doctor_101 Over a year ago

@RAZ_Muh_Taz you don't need braces with if in this condition because compiler will automatically include everything inside the if condition.

RAZ_Muh_Taz Over a year ago

how does it know to include everything under the if? this isn't python so i wouldn't think the spaces identify them as being part of the if @nitinsh99

|

Ryan Gee · Accepted Answer · 2016-12-07 19:16:58Z

1

Could you do:

var fastest = '';
var fastestIndex = '';

for (int i = 0; i < array.length; i++) {
    if(times[i] < fastest)
        fastest = times[i];
        fastestIndex = i;
}

Then use:

names[fastestIndex]

to get the name?

answered Dec 7, 2016 at 19:16

Ryan Gee

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Comments

Daniel · Accepted Answer · 2016-12-07 19:25:43Z

1

int minimum = 0;
for(int i = 1; i < times.length; i++){
    if(times[minimum] > times[i]){
        minimum = i;
    }
}
System.out.println(names[minimum]);

this should do the job

edited Dec 7, 2016 at 19:25

answered Dec 7, 2016 at 19:14

Daniel

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Comments

Md. Nasir Uddin Bhuiyan · Accepted Answer · 2016-12-07 19:15:09Z

0

call this way array_variable[index]

int index = 0;
for (int i = 0; i < array.length; i++) {
 if(times[i] < fastest){
    fastest = times[i];
    index = i;
 }
}
System.out.println(names[index]);

answered Dec 7, 2016 at 19:15

Md. Nasir Uddin Bhuiyan

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Comments

Vadim Beskrovnov · Accepted Answer · 2016-12-07 19:24:27Z

0

The simplest way for this case:

int index = 0;
for (int i = 0; i < array.length; i++) {
    if(times[i] < fastest) {
        fastest = times[i];
        index = i;
    }
}
System.out.println(names[index]);

But it will be better, if you use Map, that contains pair of name and number.

edited Dec 7, 2016 at 19:24

answered Dec 7, 2016 at 19:15

Vadim Beskrovnov

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Comments

Naman · Accepted Answer · 2016-12-07 19:37:11Z

0

Simply use a field to track the index as :

int indexOfFastest = 0;
int fastest = Integer.MAX_VALUE; // this initialization makes sure first element is assigned to fastest within the iteration
for (int i = 0; i < array.length; i++) {
    if(times[i] < fastest) {
        fastest = times[i];
        indexOfFastest = i;
    }
}

and further modify your existing code as

System.out.println(Arrays.asList(names).get(indexOfFastest));

Edit - Since the code with converting into a List ends up running the same evaluation as getting the values of array element at an index. Please prefer using

System.out.println(names[indexOfFastest]);

instead for better practices.

edited Dec 7, 2016 at 19:37

answered Dec 7, 2016 at 19:18

Naman

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4 Comments

Bernhard Barker Over a year ago

Rather names[indexOfFastest] than Arrays.asList(names).get(indexOfFastest)

Naman Over a year ago

@Dukeling sure. please throw some light on why?

Bernhard Barker Over a year ago

I guess I could say something about writing more code which calls 2 methods and constructs a class, and ultimately just ends up running the same code as the former on top of that, but I guess it's more just a best-practices issue.

Naman Over a year ago

@Dukeling Okay :) I get that.

hasham.98 · Accepted Answer · 2016-12-07 19:39:49Z

0

It worked for me

int fastest=0;
        for (int i = 1; i < times.length; i++) {
            if(times[i] < times[fastest])
                fastest = i;}
        System.out.println("Fastest runner is "+names[fastest]);

answered Dec 7, 2016 at 19:39

hasham.98

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