Thread: find closest number in array

  1. #1
    Registered User
    Join Date
    Aug 2015
    Posts
    73

    find closest number in array

    i want to make program to find closest number in array
    ex. if array elements are 2,7,78 and user types 89 then nearest element to 89 is 78 so it should print 78 but it prints 100
    why?
    i think program is adding 89 to 11 where 11 is minimum differnce between number and array element but program is not checking wheheather this number is present in array or not. if number is not present then i print 2*min + b but still output is 100
    can someone give me code for this program? here is my code

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include<string.h>
    
    
    int main()
    {
    int a[100],i,j,n,no,s[100],min,b,flag;
    printf("How many no");
    scanf("%d",&n);
    printf("Enter elements");
    for(i=0;i<n;i++)
        scanf("%d",&a[i]);
    printf("Enter to search closest element");
    scanf("%d",&no);
    for(i=0;i<n;i++)
     {
        if(no<a[i])
        s[i]=a[i]-no;
        else
            s[i]=no-a[i];}
            min=s[0];
            for(i=1;i<n;i++)
            {
              if(s[i]<min)
              min=s[i]; }
                b=no-min;
                for(i=0;i<n;i++)
                if(b==s[i])
                {
                    flag=1;
                    break;
                }
                if(flag==1)
                    printf("%d",b);
                    else
                    printf("%d",2*min+b);
    
    
    }
    Last edited by san12345; 06-19-2016 at 12:46 AM.

  2. #2
    and the hat of int overfl Salem's Avatar
    Join Date
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    Posts
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    First off, learn how to indent code consistently.
    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include<string.h>
    
    int main()
    {
      int a[100], i, j, n, no, s[100], min, b, flag;
      printf("How many no");
      scanf("%d", &n);
    
      printf("Enter elements");
      for (i = 0; i < n; i++)
        scanf("%d", &a[i]);
    
      printf("Enter to search closest element");
      scanf("%d", &no);
    
      for (i = 0; i < n; i++) {
        if (no < a[i])
          s[i] = a[i] - no;
        else
          s[i] = no - a[i];
      }
    
      min = s[0];
      for (i = 1; i < n; i++) {
        if (s[i] < min)
          min = s[i];
      }
    
      b = no - min;
      for (i = 0; i < n; i++)
        if (b == s[i]) {
          flag = 1;
          break;
        }
    
      if (flag == 1)
        printf("%d", b);
      else
        printf("%d", 2 * min + b);
    }
    Next, learn how to use a debugger.
    For example, put a breakpoint on the final if ( flag == 1 ), and look around.
    Code:
    $ gdb -q ./a.out 
    Reading symbols from /home/sc/Documents/a.out...done.
    (gdb) b 38
    Breakpoint 1 at 0x4006f2: file bar.c, line 38.
    (gdb) run
    Starting program: /home/sc/Documents/a.out 
    How many no3
    Enter elements2 7 78
    Enter to search closest element89
    
    Breakpoint 1, main () at bar.c:38
    38        if (flag == 1)
    (gdb) print flag
    $1 = 0
    (gdb) print min
    $2 = 11
    (gdb) print b
    $3 = 78
    > printf("%d", 2 * min + b);
    Well duh!
    min is 11 and b is 78, so sure you get 100 printed.

    Perhaps you need to examine your algorithm.

    FWIW, your min should be -11, that would fix it.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

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