Given a desired number, this snippet generates a random array (0<values<1) and outputs the index of the array with value nearest the given float

search_array.c

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>





int search(double xref, size_t length, double *x) {
    /* 
    Returns the index corresponding to the element in array x with
    value nearest xref.
    
    Inspired on https://codereview.stackexchange.com/a/5146/161148
    */
    int i, minindex;
    double *diff;
    double minimum;

    // defines array diff=|x-xref|
    diff = (double *)malloc(sizeof(double)*length);
    for (i = 0; i < length; i++){
    	diff[i] = fabs(x[i]-xref);
    }

    // starting values for search
    minimum = diff[0];
    minindex=0;

    // minimum search
    for (i = 1; i < length; ++i) {
        if (minimum > diff[i]) {
            minimum = diff[i];
            minindex=i;
        }
    }

    return minindex;
}









int main(int argc, char *argv[]) {
	/*
	Given the desired float, this code generates a random array and
	outputs the index of the array with value nearest the given float.
	*/

    int i, j, n=1000;
    double *ran;
    float arg;

    // handle command-line argument
    if ( argc != 2 ) {
    	printf( "usage: %s float \n", argv[0] );
    	exit(0);
    } 
    
    sscanf(argv[1], "%f", &arg); // reads command-line argument

    // generates array of random floats
    ran = (double *)malloc(sizeof(double)*n);     
    srand(time(NULL)); 
    for (i = 0; i < n; i++){
         ran[i] = ((double)rand()/(double)(RAND_MAX));
   }

   // finds index of element in ran closest to given value fx
   j=search(arg,n,ran);

   printf("Given value %f, \n Nearest value x[%i]=%f \n", arg, j, ran[j]);




    return(0);
}