Finding common minimum value between two arrays

Question

I am working on a problem in Javascript. Finding common minimum value between two arrays. However, I have been told that this might not work on some values. What is the issue?

function cmp(a, b) { return a - b; }

function findMinimum(A, B) {
    var n = A.length;
    var m = B.length;
    A.sort(cmp);
    B.sort(cmp);
    var i = 0;
    for (var k = 0; k < n; k++) {
        if (i < m - 1 && B[i] < A[k])
            i += 1;
        if (A[k] == B[i])
            return A[k];
    }
    return -1;
}

Because I need to return the minimum number which is to be found in both arrays. If A[0] and B[0] are different, that will not help. — Vintage, Aug 05 '15 at 09:38
try to consider this answer http://stackoverflow.com/questions/31828623/finding-common-minimum-value-between-two-arrays/31828954#31828954 — Neil Villareal, Aug 05 '15 at 09:53
All you just need to do is merge, sort then get the first index — Neil Villareal, Aug 05 '15 at 09:54

ripr · Answer 1 · 2015-08-05T10:34:51.193

This should work. Just replace the first if with a while. The while loop loops through array B till it finds an element which is greater than the minimum element of A. Then the outer for loop loops through A to find any element that matches the current element of B or till it reaches an element that is greater than the current element of B, where the process repeats.

function cmp(a, b) {
  return a - b;
}

function findMinimum(A, B) {
  var n = A.length;
  var m = B.length;
  A.sort(cmp);
  B.sort(cmp);
  var i = 0;
  for (var k = 0; k < n; k++) {
    while (i < m - 1 && B[i] < A[k])
      i += 1;
    if (A[k] == B[i])
      return A[k];
  }
  return -1;
}

findMinimum([1,3,5,7], [0,0,1,4,9]);  // 1
findMinimum([3,5,7,9], [1,2,4,7,10]); // 7

Codebender · Answer 2 · 2015-08-05T09:53:29.833

5

Let's take,

A = [ 1, 3, 5, 7]
B = [ 0, 0, 1, 4, 6]

and run through your loop.

Your script fails.

The correct logic should be, you either increment i or k in 1 iteration. Not both

I would do something like,

for (var k = 0; k < n;) {
    if (A[k] == B[i])
        return A[k];

    if (i < m - 1 && B[i] < A[k])
        i += 1;
    else
        k += 1;
}

edited Aug 05 '15 at 09:53

answered Aug 05 '15 at 09:42

Codebender

14,221
7
48
85

This is the answer, sir. Thank you. – Vintage Aug 05 '15 at 10:01

score 3 · Answer 3 · answered Aug 05 '15 at 09:38

3

I'd suggest changing your methodology here. Sorting both of the arrays at the beginning is expensive. Find the intersection set of two arrays and then sort it and return its mimimum value, that's all.

answered Aug 05 '15 at 09:38

Juvanis

25,802
5
69
87

I am going to mark this an answer. Thank you. However, is there any way you can modify my code in at most two lines? That is how I am supposed to do it. I know intersection is better, but I am supposed to use loops for some weird reason... – Vintage Aug 05 '15 at 09:42
_"supposed to do it"_? Is this a school assignment? – Cerbrus Aug 05 '15 at 09:46
I am working on programming challenges from a student book. – Vintage Aug 05 '15 at 09:48

score 0 · Answer 4 · answered Aug 21 '21 at 15:07

// java code for this 
import java.util.Arrays;

public class CommonMinValue {

public static void main(String[] args) {
    int [] A = {1,5,6,7,8,9,11};
    int [] B = {11,51,16,7,18,19,161};
    
    int n = A.length;
    int m = B.length;;
    Arrays.sort(A);
    System.out.println(Arrays.toString(A));
    System.out.println(Arrays.toString(B));
    Arrays.sort(B);
    int commMin=-1;
    
    int i = 0;
    for (int k = 0; k < n;) {
         if (A[k] == B[i]) {
            commMin = A[k];
            break;
         }
        if (i < m - 1 && B[i] < A[k])
            i ++;
        else
            k ++;
       
    }
   System.out.println("Common minimum value "+commMin);
   
}

}

Finding common minimum value between two arrays

4 Answers4

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