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Subject description:
Topic Title: prefix judge
The following code determines whether the string pointed needle_start prefix string haystack_start points, if not, NULL is returned.
For example: "abcd1234" contains the "abc" as a prefix
char* prefix(char* haystack_start, char* needle_start)
{
char* haystack = haystack_start;
char* needle = needle_start;
while(*haystack && *needle){
if(______________________________) return NULL; //填空位置
}
if(*needle) return NULL;
return haystack_start;
}
Analyze code logic, and speculated that crossed at the code, submitted via the web.
Note: Only the lack of code as the answer, do not fill in the extra code symbols or caption! !
solution:
#include<iostream>
using namespace std;
char* prefix(char* haystack_start, char* needle_start)
{
char* haystack = haystack_start;
char* needle = needle_start;
while(*haystack && *needle){
// if( haystack++ == needle++ ) return NULL; //填空位置
if(*(haystack++) != *(needle++)) return NULL;
}
if(*needle) return NULL;
return haystack_start;
}
int main(){
printf("%s",prefix("abcd123","abc"));
return 0;
}