Hi,
I've written a substring function.
The prototype is: int substr(char s1[], char s2[])
Returns 1 if s2 is a substring of s1, else it returns 0.
I have written this program, but Im sure there is an easier way to do this. I am hoping someone can point me to a more elegant way of writing this same function.
//// code follows ///////////
//implement a substring function, where if string2 is a sub of string 1, then the value returned is 1 else, 0
#include<iostream>
#include<cstring>
using namespace std;
const int MAX = 10;
int substring(char *str1, char *str2); //prototype
int main()
{
char response = 'y';
char str1[MAX];
char str2[MAX];
int result = 0;
while(response == 'Y' || response == 'y')
{
cout << "Please enter string 1: " ;
cin >> str1;
cout << "\nPlease enter string 2: ";
cin >> str2;
cout << endl;
result = substring(str1, str2); //function call
if(result == 1)
cout << "string " << str2 << " is a substring of " << str1 << endl;
else
cout << "string " << str2 << " is NOT a substring of " << str1 << endl;
cout << "would you like to enter another? (Y/N) " << endl;
cin >> response;
}
return 0;
}
//''''''''''''''''''''''''''''''''''''''''''
//Function definition substring
int substring(char *str1, char *str2)
{
int len1, len2, i=0, j = 0, k, n;
len1=strlen(str1); //determine the lengths of the strings
len2=strlen(str2);
while(i <len1)
{
while( str2[j] == str1[i] )
{
for(k=1, n=i+1; k<len2; k++, n++)
//n is assigned i, which is where the match //starts in string 1- starting at the next letter
{
if( str2[k] != str1[n] )
return 0; //the match fails after having made an initial match
}
return 1;
j++;
}
i++;
}
} 7 8554
"Radhika Sambamurti" <ra*****@schemamania.org> wrote in message
news:20040220152353.3c0d3e87.ra*****@schemamania.o rg... Hi, I've written a substring function. The prototype is: int substr(char s1[], char s2[]) Returns 1 if s2 is a substring of s1, else it returns 0. I have written this program, but Im sure there is an easier way to do
this. I am hoping someone can point me to a more elegant way of writing this
same function.
Why not use the std::string member functions?
find( )
find_first_of( )
find_last_of( )
find_first_not_of( )
find_last_not_of( )
rfind( )
These return the starting position of the where the match is found, or a -1
cast to unsigned int if no match is found.
How about this:
int substring(char *str1, char *str2)
{
return (strstr(str1, str2) != NULL);
}
-jj-
Radhika Sambamurti wrote: Hi, I've written a substring function. The prototype is: int substr(char s1[], char s2[]) Returns 1 if s2 is a substring of s1, else it returns 0. I have written this program, but Im sure there is an easier way to do this. I am hoping someone can point me to a more elegant way of writing this same function.
//// code follows ///////////
//implement a substring function, where if string2 is a sub of string 1, then the value returned is 1 else, 0
#include<iostream> #include<cstring> using namespace std;
const int MAX = 10; int substring(char *str1, char *str2); //prototype
int main() { char response = 'y'; char str1[MAX]; char str2[MAX]; int result = 0;
while(response == 'Y' || response == 'y') { cout << "Please enter string 1: " ; cin >> str1;
cout << "\nPlease enter string 2: "; cin >> str2;
cout << endl;
result = substring(str1, str2); //function call
if(result == 1) cout << "string " << str2 << " is a substring of " << str1 << endl; else cout << "string " << str2 << " is NOT a substring of " << str1 << endl;
cout << "would you like to enter another? (Y/N) " << endl; cin >> response;
}
return 0; }
//'''''''''''''''''''''''''''''''''''''''''' //Function definition substring
int substring(char *str1, char *str2) { int len1, len2, i=0, j = 0, k, n; len1=strlen(str1); //determine the lengths of the strings len2=strlen(str2);
while(i <len1) {
while( str2[j] == str1[i] ) {
for(k=1, n=i+1; k<len2; k++, n++)
//n is assigned i, which is where the match //starts in string 1- starting at the next letter
{ if( str2[k] != str1[n] ) return 0; //the match fails after having made an initial match } return 1;
j++; }
i++; }
}
Radhika Sambamurti wrote: Hi, I've written a substring function. The prototype is: int substr(char s1[], char s2[]) Returns 1 if s2 is a substring of s1, else it returns 0.
Why? Is this for a school exercise, or self-teaching? The above function
is almost, but not quite, the same as the C standard function strstr().
Why even mess with C-style strings?
I have written this program, but Im sure there is an easier way to do this. I am hoping someone can point me to a more elegant way of writing this same function.
int substr(char s1[], char s2[])
{
if (strstr (s1, s2))
return 1;
return 0;
}
;)
int substring(char *str1, char *str2) { int len1, len2, i=0, j = 0, k, n; len1=strlen(str1); //determine the lengths of the strings len2=strlen(str2);
These calls to strlen() are going to whack your efficiency. They
terminate C-style strings for a reason, use that in your routine. You
don't need to know the lengths, just the endpoints. while(i <len1) {
while( str2[j] == str1[i] ) {
for(k=1, n=i+1; k<len2; k++, n++)
//n is assigned i, which is where the match //starts in string 1- starting at the next letter
{ if( str2[k] != str1[n] ) return 0; //the match fails after having made an initial match } return 1;
j++; }
i++; }
}
Here's one to consider:
int substr(const char *string, const char *substring)
{
const char *a = string;
const char *b = substring;
b = substring;
if (*b == 0)
{
return 1;
}
for ( ; *string != 0; string += 1)
{
if (*string != *b)
{
continue;
}
while (1)
{
if (*b == 0)
{
return 1;
}
if (*a++ != *b++)
{
break;
}
}
}
return 0;
}
Brian Rodenborn
Default User wrote: int substr(const char *string, const char *substring) { const char *a = string; const char *b = substring;
b = substring;
The above line is superfluous and should have been removed when I move
the assignments up to initializers.
Sorry.
Brian Rodenborn
On Fri, 20 Feb 2004 22:16:39 GMT
Default User <fi********@boeing.com.invalid> wrote: Radhika Sambamurti wrote: Hi, I've written a substring function. The prototype is: int substr(char s1[], char s2[]) Returns 1 if s2 is a substring of s1, else it returns 0.
Why? Is this for a school exercise, or self-teaching? The above function is almost, but not quite, the same as the C standard function strstr().
Thanks! Yes, this was a class exercise. These return the starting position of the where the match is found, or a -1 cast to unsigned int if no match is found.
I know that this is practically irrelevant, but the correct return value
is std::string::npos, not -1.
Radhika Sambamurti wrote: On Fri, 20 Feb 2004 22:16:39 GMT Default User <fi********@boeing.com.invalid> wrote:
Radhika Sambamurti wrote: Hi, I've written a substring function. The prototype is: int substr(char s1[], char s2[]) Returns 1 if s2 is a substring of s1, else it returns 0.
Why? Is this for a school exercise, or self-teaching? The above function is almost, but not quite, the same as the C standard function strstr(). Thanks! Yes, this was a class exercise.
Ok. What you had wasn't too bad, although much more appropriate for a C
class than C++. I'm suspicious of the quality of instruction you are
getting.
Brian Rodenborn This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics
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