Find the index of two minimum values in array

Question

I have an array that contains numbers.

I got the two minimum values (can be the same number) of this array in O(N) but i cant figure out how to get the index of this two values.

For example: in {1,2,3,1,5} the answer will be index 0 and index 3. this is the code i'm using:

    public static void minMin(int arr[]){
    int min1 = weights[0], min2 = weights[1];
      if(min1 > min2){
       int temp = min1;
       min1 = min2;
       min2 = temp;
      }
      for (int i = 2; i < weights.length; i++) {
       if(weights[i] < min1){
        int temp = min1;
        min1 = weights[i];
        min2 = temp;
       }else if(weights[i] < min2){
        min2 = weights[i];
       }
      }
}

See [this question](https://stackoverflow.com/questions/6171663/how-to-find-index-of-int-array-in-java-from-a-given-value). — ack, Jun 04 '17 at 17:03
For the record : I updated my answer a bit ;things are even simpler. But again, I didn't drop code, as I am not here to do your homework. I just try to help you doing it yourself. — GhostCat, Jun 04 '17 at 18:30

GhostCat · Answer 1 · 2017-06-04T17:48:28.363

5

In addition to the local variables that keep the minimum values you need variables for the indexes, too.

You initiatilaze them with 0/1 and update them whenever you change the other variables.

Further thinking about this: one other option works without more variables. Storing value + index is convenient (the comment is correct though, you would probably use a distinct class to do that) but not mandatory. Because you can always fetch the value when you have an index!

In that sense: you could change your code to remember indixes only.

edited Jun 04 '17 at 17:48

answered Jun 04 '17 at 17:02

GhostCat

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I have only one index because its one for loop and i need the index's of two elements.. – Nauruto Jun 04 '17 at 17:09
No, ghostcat is right. You just have to store the values in variables – Dennux Jun 04 '17 at 17:16
Simple and efficient as usualy :) – davidxxx Jun 04 '17 at 17:27

score 1 · Accepted Answer · answered Jun 04 '17 at 17:16

Ghostcat already gave the answer, you just didnt understand:

I have only one index because its one for loop and i need the index's of two elements..

Just create more variables:

public static void main(String[] args) {

    minMin(new int[] { 1, 2, 3, 1, 5 });
}

// Careful: this code only works for arr.lengh > 1
public static void minMin(int arr[]) {

    int min1 = arr[0];
    int min2 = arr[1];

    int index1 = 0;
    int index2 = 1;

    if (min1 > min2) {
        int temp = min1;
        min1 = min2;
        min2 = temp;

        index1 = 1;
        index2 = 0;
    }

    for (int i = 2; i < arr.length; i++) {
        if (arr[i] < min1) {
            int temp = min1;
            min1 = arr[i];
            min2 = temp;
            index2 = index1;
            index1 = i;
        } else if (arr[i] < min2) {
            min2 = arr[i];
            index2 = i;
        }
    }

    System.out.println("Smallest: " + min1 + ", index " + index1);
    System.out.println("2nd smallest: " + min2 + ", index " + index2);
}

Output:

Smallest: 1, index 0
2nd smallest: 1, index 3

I personally would create a class for holding the values and storing the values to keep the logic of the algorithm clear from the logic of the storing. It would also help to divide the task into two smaller, easier tasks. But that's just my opinion. — Dennux, Jun 04 '17 at 17:18
For the record: I don't mind that you received the accept, but: it is discouraged to do all parts of homework question. I tried to give the op some hints to enable him solving it himself. You conveniently solved it for him. So you actually robbed the op from making important learning steps :-) — GhostCat, Jun 04 '17 at 18:33

Find the index of two minimum values in array

2 Answers2