CODEWITHSUNDEEP
javaarraysintegerrounding
blazma
blazma

Reputation: 35

Rounding an integer to specific integers in Java

I have a small problem, but I hope somebody can help. Let's say that I have an array of integers, something like this:

int[] = {65, 75, 85}

And the program takes an integer input from the user, and the output will be the closest number from the array.

For example: If the user inputs 68, the output will be 65, since 65 is the closest number. Or if the user inputs 100 the output will be 85, since 85 is the closest.

EDIT: This is NOT homework. I program for myself not for anyone else :P

Thanks in advance, Martin

Upvotes: 1

Views: 517

Answers (3)

Peter Lawrey
Peter Lawrey

Reputation: 533680

If the array is sorted, a more efficient approach is to use a binary search. This takes O(log n) time instead of O(n) elements, as it doesn't need to examine every value.

public static void main(String... args) {
    int[] values = {65, 75, 85};
    for (int find : new int[]{60, 68, 74, 88}) {
        int result = closest(find, values);
        System.out.println(find + " => " + result);
    }
}

private static int closest(int find, int... values) {
    int index = Arrays.binarySearch(values, find);
    if (index >= values[0])
        return index;
    if (index == -1)
        return values[0]; // closest
    index = -index - 2;
    if (index + 1 >= values.length)
        return values[values.length - 1]; // closest
    final int v0 = values[index];
    final int v1 = values[index + 1];
    return Math.abs(v0 - find) <= Math.abs(v1 - find) ? v0 : v1;
}

prints

60 => 65
68 => 65
74 => 75
88 => 85

Upvotes: 3

Bohemian
Bohemian

Reputation: 425208

The important thing is to compare the absolute differences.

Try this:

public int getClosest(int[] array, int input) {
    int lowestDiff = Integer.MAX_VALUE;
    int result = 0;
    for (int i : array) {
        int diff = Math.abs(input - i); // use API to get absolute diff
        if (diff < lowestDiff) {
            lowestDiff = diff;
            result = i;
        }
    }
    return result;
}

This code will return 0 if the array is empty.

Note: It is possible the input and array element is more than Integer.MAX_VALUE apart. You may want to code for this.

Upvotes: 2

Guillaume Polet
Guillaume Polet

Reputation: 47607

public int getClosest(int input) {
    int ret = -1;
    for(int i=;i<array.length;i++) {
       if (ret==-1 || Math.abs(array[i]-input)<Math.abs(array[ret]-input)) {
            ret = i;
       }
    }
    if (ret>-1)
         return array[ret];
    else
       // To do
}

Upvotes: 0

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