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Closed 12 years ago.
Not counting the function signature (just the body) can anybody produce C code shorter than this function that will reverse a string and return the result as a pointer to the reversed string.. (not using a string reverse library function either)?
char * reverse_str(char * s)
{
char c,*f=s,*p=s;while(*p)p++;while(--p>s){c=*p;*p=*s;*s++=c;}return f;
}
not much longer, but it works.
#include <string.h>
/* precondition: s!=const && s!=NULL && *s!='\0' */
char *mystrrev(char *s)
{
char *a=s,*e=s+strlen(s)-1;
while( a<e )
{
char c=*a;
*a++=*e;
*e--=c;
}
return s;
}
Related
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Closed 9 years ago.
I have a byte array (dB). I am trying to extract the bytes one by one. Why isn't this code working? Any pointers? Logically am I wrong? Or something wrong with my implementation?
You have byte buffers declared like this:
unsigned char *decodeBuf;
To read a single value from that buffer, at offset i you simply write:
unsigned char b = decodeBuf[i];
try
int main()
{
unsigned char tmp;
tmp = getByte(dB+dOffset); dOffset++;
}
it should work
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Closed 9 years ago.
Can anyone help me convert the C code below to MIPS code? I'm supposed to use recursion and get 21 - 2 as the final answer. Thanks!
/*
x is a pointer to a linked list node and is not null.
Return the min value stored in the linked list.
Assume each node is stored in memory as an int (value) followed by a pointer to the next node (next), each a word wide.
You must write it with recursion. */
int findMin(node *x) {
if(x->next == NULL)
return x->value;
else {
int min = findMin(x->next);
if(min < x->value)
return min;
else
return x->value;
}
}
Here you are:
mips-linux-gnu-gcc -S -o foo.asm foo.c
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Closed 10 years ago.
I have an array of chars "0x55".
What I want to do is convert it to a char which is going to be U (because ASCII 0x55 = U).
So how to do this conversion?
#include <windows.h>
int main()
{
array[] = "0x55"
char test;
**// I want to move the string to that test to be one character which is U**
}
Any suggestions?
I think this is what you are after:
int main(int argc,char**argv)
{
char array[] = "0x55";
int value;
char test;
sscanf(array,"%x",&value);
test = value;
return 0;
}
In C++, I would code it a little differently, but this seems more like a C question.
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Closed 11 years ago.
here is a general implementation
int stridx (char[] src, char[] str){
int i,j,k;
for(i=0;i < (src.len - str.len);i++){
for(j=i,k=0; str[k] != '\0' && str[k] == src[i]; j++,k++);
if( k> 0 && str[k]=='\0') return i;
}
return -1;
}
The worst case of the algorithm could be n^2, if we have aaaaaaaaaaaaaaaaaaaaaaaa (assuming both src and str are very long, and the length of them is very close).
Can I have a better algorithm?
You could use the Boyer-Moore algorithm, which is O(n). Here's sample C code.
It's not necessary to calculate the length of the strings :
char *strr(char *s1,char *s2)
{
int i,j;
for(i=0;s1[i];i++)
if(s1[i]==s2[0])
for(j=0;s1[i+j]==s2[j];j++)
if(!s2[j+1]) return &s1[i];
return NULL;
}
http://en.wikipedia.org/wiki/Knuth%E2%80%93Morris%E2%80%93Pratt_algorithm is another linear time algorithm. OTOH, the simple algorithms stay because in practise they are faster for most of the strings people actually search with.
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Closed 12 years ago.
i am learning C programming, i was trying to write a recursive function by using this prototype:
void fact(int *n);
The parameter of this function should be passed by reference. Thanks for your help.
I don't feel to be helpful in giving a complete solution -- this is just to show there is an answer:
void fact(int *n)
{
if (*n > 1)
{
int tmp = *n - 1;
fact(&tmp);
*n *= tmp;
}
}
I would never write a factorial function this way.