Binary search in C language [closed] - c

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What is the problem with the next code ?
It is a code for making a binary search between the elements of an array that we fill randomly using the rand() function. We use here the function bin_sear to sort and return for us a boolean value true if the element we seek is found in our table and flase if the element we dont find doesent figure in our table. The code doesent work. So where is the error here ?
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
typedef enum { false, true } bool;
bool bin_sear(int k[] ,int s , int target );
int main()
{
int a[10];
int i,j;
char k;
bool bin;
while(1){
srand(time(NULL));
// we fill our table
for(i=0;i<10;i++){
a[i]=rand()%101+1;
}
printf("Please enter the element you are seeking for: ");
scanf("%d",&j);
if(bin_sear(a[10],10,j)==true){
printf("The element you seek exists in our array");
}
else {
printf("The element you are seeking doesent exist in our array");
}
if (k=='n'){
break;
}
}
return 0;
}
bool bin_sear(int k[],int s, int target){
int i,j,pos,aux,low,high,test;
for (i=0;i<s;i++){
pos=i;
for (j=i;j<s;j++){
if (k[j]<pos){
pos=j;
}
aux=k[pos];
k[pos]=k[i];
k[i]=aux;
}
}
low=0;
high=s;
while (low<high-1){
test=(low+high)/2;
if (target<k[test]){
high=test;
}
else low=test;
}
if (target==k[test]){
return true;
}
else return false;
}

Answer 1

A number of errors in your code.
You need to call bin_sear with the pointer to the array, not element a[10] (which will give you an immediate segmentation fault):
if(bin_sear(a[10],10,j)==true){
should be
if(bin_sear(a,10,j)==true){
Next - take a look at your bubble sort routine. You have the indices wrong, and the braces in the wrong place, and you are comparing a value to an index with your if statement. Modify it to this, and you will get a sorted array:
for (i=0;i<s-1;i++){
pos=i;
for (j=i+1;j<s;j++){
if (k[j]<k[i]){
pos=j;
aux=k[pos];
k[pos]=k[i];
k[i]=aux;
}
}
}
Next, you don't seem to set the value of k anywhere, so you have an infinite loop. Fix all that, and things will work a little bit better. Recommend you put a lot of printf statements in your code if this is not enough (and use a smaller range of random numbers initially to improve your chances of a hit).
Working code:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
typedef enum { false, true } bool;
bool bin_sear(int k[] ,int s , int target );
int main()
{
int a[10];
int i,j;
char k;
bool bin;
while(1){
srand(time(NULL));
// we fill our table
for(i=0;i<10;i++){
a[i]=rand()%10+1;
}
printf("Please enter the element you are seeking for: \n");
// scanf("%d", &j); // not scanning input since this is codepad
j = 5;
printf("you entered: %d\n", j);
fflush(stdout);
if(bin_sear(a,10,j)==true){
printf("The element [%d] exists in our array\n", j);
}
else {
printf("The element [%d] doesn't exist in our array\n", j);
printf("The array contains:\n");
for(i = 0; i < 9; i++) printf("%d, ", a[i]);
printf("%d\n", a[9]);
}
printf("Would you like to test for another element?\n");
// k = getchar();
k = 'N'; // simulating user pressing uppercase N
if(tolower(k) == 'n') {
printf("goodbye!\n");
break; // do this only once
}
}
return 0;
}
bool bin_sear(int k[],int s, int target){
int i,j,pos,aux,low,high,test;
printf("starting to sort\n");
fflush(stdout);
for (i=0;i<s-1;i++){
pos=i;
for (j=i+1;j<s;j++){
if (k[j]<k[i]){
printf("swapping %d and %d\n", i, j); fflush(stdout);
pos=j;
aux=k[pos];
k[pos]=k[i];
k[i]=aux;
}
}
}
printf("sort finished\n");
printf("elements now:\n");
for(i = 0; i < s; i++) printf("k[%d] = %d\n", i, k[i]);
fflush(stdout);
low=0;
high=s;
while (low<high-1){
test=(low+high)/2;
if (target<k[test]){
high=test;
}
else low=test;
}
if (target==k[test]){
return true;
}
else return false;
}

Answer 2

if(bin_sear(a[10],10,j)==true){ => if(bin_sea(a, 10, j) == true) from a quick glance. You need to pass the array into the function, a[10] would try to index the eleventh elment of the array, is also the wrong type (being an int instead of an array), and will probably cause an access violation exception, because the array is only ten elements long. Lots of errors for four characters, eh?

Answer 3

It makes no sense to write a function which sorts the array and then makes the binary search. You should separate the two algorithms, otherwise a linear search would be more efficient.