CODEWITHSUNDEEP
clookup-tables
uniquenamehere
uniquenamehere

Reputation: 1949

Lookup table for keys that are of the form k = 2^n with array size of n

I want to make a lookup-table/array.

The index values I get are of the form k = 2^n only, where n is an integer. So I want to reduce the arrays size to n and I therefore have to perform an operation on the index values as well.

I want the most efficient way to do this as I am programming on an embedded platform.

Example:

I got the values n = {1, 2, 4, 8, 16, 32}

I have an array defined as:

int myArray[6];

Now I want to convert the values n to m, where m = {1, 2, 3, 4, 5, 6} so I can access array elements:

myArray[m];

Upvotes: 0

Views: 84

Answers (1)

Iharob Al Asimi
Iharob Al Asimi

Reputation: 53016

This is a solution

#include <stdio.h>

int main()
{
    int array[6] = {1, 2, 4, 8, 16, 32};
    int index[6];
    int i;

    for (i = 0 ; i < 6 ; i++)
    {
        int value;

        value    = array[i];
        index[i] = 0;
        while ((value >>= 1) != 0)
            index[i] += 1;
        printf("%d\n", index[i]);
    }
    return 0;
}

Upvotes: 1

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