String matching
Given two strings, demonstrate the following 3 types of matchings:
- Determining if the first string starts with second string
- Determining if the first string contains the second string at any location
- Determining if the first string ends with the second string
You are encouraged to solve this task according to the task description, using any language you may know.
Optional requirements: A) Print the location of the match for part 2 B) Handle multiple occurrences of a string for part 2.
ALGOL 68
<lang algol68># define some appropriate OPerators # PRIO STARTSWITH = 5, ENDSWITH = 5; OP STARTSWITH = (STRING str, prefix)BOOL: # assuming LWB = 1 #
IF UPB str < UPB prefix THEN FALSE ELSE str[:UPB prefix]=prefix FI;
OP ENDSWITH = (STRING str, suffix)BOOL: # assuming LWB = 1 #
IF UPB str < UPB suffix THEN FALSE ELSE str[UPB str-UPB suffix+1:]=suffix FI;
INT loc, loc2;
print((
"abcd" STARTSWITH "ab", # returns TRUE # "abcd" ENDSWITH "zn", # returns FALSE # string in string("bb",loc,"abab"), # returns FALSE # string in string("ab",loc,"abab"), # returns TRUE # (string in string("bb",loc,"abab")|loc|-1), # returns -1 # (string in string("ab",loc,"abab")|loc|-1), # returns +1 # (string in string("ab",loc2,"abab"[loc+1:])|loc+loc2|-1) # returns +3 #
))</lang> Output:
TFFT -1 +1 +3
C++
<lang cpp>
- include <string>
using namespace std;
string s1="abcd"; string s2="abab"; string s3="ab"; //Beginning s1.compare(0,s3.size(),s3)!=0; //End s1.compare(s1.size()-s3.size(),s3.size(),s3)!=0; //Anywhere s1.find(s2)//returns string::npos int loc=s2.find(s3)//returns 0 loc=s2.find(s3,loc+1)//returns 2 </lang>
Java
<lang java> "abcd".startsWith("ab") //returns true "abcd".endsWith("zn") //returns false "abab".contains("bb") //returns false "abab".contains("ab") //returns true int loc = "abab".indexOf("bb") //returns -1 loc = "abab".indexOf("ab") //returns 0 loc = "abab".indexOf("ab",loc+1) //returns 2 </lang>
Objective-C
<lang objc> [@"abcd" hasPrefix:@"ab"] //returns true [@"abcd" hasSuffix:@"zn"] //returns false int loc = [@"abab" rangeOfString:@"bb"].location //returns -1 loc = [@"abab" rangeOfString:@"ab"].location //returns 0 loc = [@"abab" rangeOfString:@"ab" options:0 range:NSMakeRange(loc+1, [@"abab" length]-(loc+1))].location //returns 2 </lang>
Python
<lang python> "abcd".startswith("ab") #returns true "abcd".endswith("zn") #returns false "bb" in "abab" #returns false "ab" in "abab" #returns true loc = "abab".find("bb") #returns -1 loc = "abab".find("ab") #returns 0 loc = "abab".find("ab",loc+1) #returns 2 </lang>
Tcl
In this code, we are looking in various ways for the string in the variable needle in the string in the variable haystack. <lang tcl>set isPrefix [string equal -length [string length $needle] $haystack $needle] set isContained [expr {[string first $needle $haystack] >= 0}] set isSuffix [string equal $needle [string range $haystack end-[expr {[string length $needle]-1}] end]]</lang>
Of course, in the cases where the needle is a glob-safe string (i.e., doesn't have any of the characters “*?[” in), this can be written far more conveniently: <lang tcl>set isPrefix [string match $needle* $haystack] set isContained [string match *$needle* $haystack] set isSuffix [string match *$needle $haystack]</lang>