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How std::find_last_of actually works?
Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 17/18, 2019 at 00:00UTC (8:00pm US/Eastern)
Data science time! April 2019 and salary with experience
The Ask Question Wizard is Live!How do I iterate over the words of a string?How do I read / convert an InputStream into a String in Java?Case insensitive 'Contains(string)'Convert bytes to a string?How do I make the first letter of a string uppercase in JavaScript?How to replace all occurrences of a string in JavaScriptWhy is “using namespace std” considered bad practice?How to check whether a string contains a substring in JavaScript?Why should C++ programmers minimize use of 'new'?How to remove the last character from a string?
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string s = "I Like C++ Tutorial";
cout << s.find_last_of("Like");
I know that find_last_of returns the last character that matches, however, it returns 16, which is the position of the letter i in Tutorial, But I'm confused because I'm searching for the last position of Like not i, I tried to remove i from the string. It returns 5 as I expected. But the question is why did it return 16?
c++ string
asked Mar 22 at 9:35
DamonDamon
212
add a comment |
string s = "I Like C++ Tutorial";
cout << s.find_last_of("Like");
I know that find_last_of returns the last character that matches, however, it returns 16, which is the position of the letter i in Tutorial, But I'm confused because I'm searching for the last position of Like not i, I tried to remove i from the string. It returns 5 as I expected. But the question is why did it return 16?
c++ string
asked Mar 22 at 9:35
DamonDamon
212
7
read the docs to see whyfind_last_ofbehaves that way, you wantrfindif you want to match a substring in a string from the end
– EdChum
Mar 22 at 9:36
add a comment |
string s = "I Like C++ Tutorial";
cout << s.find_last_of("Like");
I know that find_last_of returns the last character that matches, however, it returns 16, which is the position of the letter i in Tutorial, But I'm confused because I'm searching for the last position of Like not i, I tried to remove i from the string. It returns 5 as I expected. But the question is why did it return 16?
c++ string
asked Mar 22 at 9:35
DamonDamon
212
string s = "I Like C++ Tutorial";
cout << s.find_last_of("Like");
I know that find_last_of returns the last character that matches, however, it returns 16, which is the position of the letter i in Tutorial, But I'm confused because I'm searching for the last position of Like not i, I tried to remove i from the string. It returns 5 as I expected. But the question is why did it return 16?
c++ string
c++ string
asked Mar 22 at 9:35
DamonDamon
212
asked Mar 22 at 9:35
DamonDamon
212
asked Mar 22 at 9:35
DamonDamon
212
asked Mar 22 at 9:35
DamonDamon
212
asked Mar 22 at 9:35
DamonDamon
212
212
7
read the docs to see whyfind_last_ofbehaves that way, you wantrfindif you want to match a substring in a string from the end
– EdChum
Mar 22 at 9:36
add a comment |
7
read the docs to see whyfind_last_ofbehaves that way, you wantrfindif you want to match a substring in a string from the end
– EdChum
Mar 22 at 9:36
7
7
read the docs to see why
find_last_of behaves that way, you want rfind if you want to match a substring in a string from the end– EdChum
Mar 22 at 9:36
read the docs to see why
find_last_of behaves that way, you want rfind if you want to match a substring in a string from the end– EdChum
Mar 22 at 9:36
add a comment |
2 Answers
2
active
oldest
votes
find_last_of finds the last character equal to one of characters in the given character sequence.
The character sequence is "Like". The last L is at position 3, the last i is at position 16, the last k is at position 4 and the the last e is at position 5. So it returned the 16, the greatest of these values.
If the character sequence was "like" instead of "Like", it would have returned 18 because the last l is at position 18.
In case no letter in the character sequence that matches any letter in the string, npos is returned.
answered Mar 22 at 9:47
P.WP.W
19.1k41860
Might want to note what it does in the case an element is not found, e.g. searching for "Likes" finds no 's'
– Caleth
Mar 22 at 9:51
add a comment |
std::find_last_of
Finds the last character equal to one of characters in str
this means when searching the string "I Like C++ Tutorial" for the string "Like" the last character that apears in both strings is "i" wich is at position 16.
when searching for a complete string use std::find
std::string s("I Like C++ Tutorial");
std::cout << s.find("Like"); // prints 2
if you want to find the last occurence of the string use std::rfind
std::string s("I Like C++ Tutorial Like");
std::cout << s.rfind("Like"); // prints 20
to get the position of the last character in the last match you just have to add the length of the string:
std::string s("I Like C++ Tutorial Like");
std::string s2("Like");
std::cout << s.rfind(s2) + s2.length(); // prints 24
answered Mar 22 at 9:55
peterzugerpeterzuger
1113
add a comment |
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2 Answers
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2 Answers
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find_last_of finds the last character equal to one of characters in the given character sequence.
The character sequence is "Like". The last L is at position 3, the last i is at position 16, the last k is at position 4 and the the last e is at position 5. So it returned the 16, the greatest of these values.
If the character sequence was "like" instead of "Like", it would have returned 18 because the last l is at position 18.
In case no letter in the character sequence that matches any letter in the string, npos is returned.
answered Mar 22 at 9:47
P.WP.W
19.1k41860
Might want to note what it does in the case an element is not found, e.g. searching for "Likes" finds no 's'
– Caleth
Mar 22 at 9:51
add a comment |
find_last_of finds the last character equal to one of characters in the given character sequence.
The character sequence is "Like". The last L is at position 3, the last i is at position 16, the last k is at position 4 and the the last e is at position 5. So it returned the 16, the greatest of these values.
If the character sequence was "like" instead of "Like", it would have returned 18 because the last l is at position 18.
In case no letter in the character sequence that matches any letter in the string, npos is returned.
answered Mar 22 at 9:47
P.WP.W
19.1k41860
Might want to note what it does in the case an element is not found, e.g. searching for "Likes" finds no 's'
– Caleth
Mar 22 at 9:51
add a comment |
find_last_of finds the last character equal to one of characters in the given character sequence.
The character sequence is "Like". The last L is at position 3, the last i is at position 16, the last k is at position 4 and the the last e is at position 5. So it returned the 16, the greatest of these values.
If the character sequence was "like" instead of "Like", it would have returned 18 because the last l is at position 18.
In case no letter in the character sequence that matches any letter in the string, npos is returned.
answered Mar 22 at 9:47
P.WP.W
19.1k41860
find_last_of finds the last character equal to one of characters in the given character sequence.
The character sequence is "Like". The last L is at position 3, the last i is at position 16, the last k is at position 4 and the the last e is at position 5. So it returned the 16, the greatest of these values.
If the character sequence was "like" instead of "Like", it would have returned 18 because the last l is at position 18.
In case no letter in the character sequence that matches any letter in the string, npos is returned.
answered Mar 22 at 9:47
P.WP.W
19.1k41860
edited Mar 22 at 9:57
answered Mar 22 at 9:47
P.WP.W
19.1k41860
answered Mar 22 at 9:47
P.WP.W
19.1k41860
answered Mar 22 at 9:47
P.WP.W
19.1k41860
19.1k41860
Might want to note what it does in the case an element is not found, e.g. searching for "Likes" finds no 's'
– Caleth
Mar 22 at 9:51
add a comment |
Might want to note what it does in the case an element is not found, e.g. searching for "Likes" finds no 's'
– Caleth
Mar 22 at 9:51
Might want to note what it does in the case an element is not found, e.g. searching for "Likes" finds no 's'
– Caleth
Mar 22 at 9:51
Might want to note what it does in the case an element is not found, e.g. searching for "Likes" finds no 's'
– Caleth
Mar 22 at 9:51
add a comment |
std::find_last_of
Finds the last character equal to one of characters in str
this means when searching the string "I Like C++ Tutorial" for the string "Like" the last character that apears in both strings is "i" wich is at position 16.
when searching for a complete string use std::find
std::string s("I Like C++ Tutorial");
std::cout << s.find("Like"); // prints 2
if you want to find the last occurence of the string use std::rfind
std::string s("I Like C++ Tutorial Like");
std::cout << s.rfind("Like"); // prints 20
to get the position of the last character in the last match you just have to add the length of the string:
std::string s("I Like C++ Tutorial Like");
std::string s2("Like");
std::cout << s.rfind(s2) + s2.length(); // prints 24
answered Mar 22 at 9:55
peterzugerpeterzuger
1113
add a comment |
std::find_last_of
Finds the last character equal to one of characters in str
this means when searching the string "I Like C++ Tutorial" for the string "Like" the last character that apears in both strings is "i" wich is at position 16.
when searching for a complete string use std::find
std::string s("I Like C++ Tutorial");
std::cout << s.find("Like"); // prints 2
if you want to find the last occurence of the string use std::rfind
std::string s("I Like C++ Tutorial Like");
std::cout << s.rfind("Like"); // prints 20
to get the position of the last character in the last match you just have to add the length of the string:
std::string s("I Like C++ Tutorial Like");
std::string s2("Like");
std::cout << s.rfind(s2) + s2.length(); // prints 24
answered Mar 22 at 9:55
peterzugerpeterzuger
1113
add a comment |
std::find_last_of
Finds the last character equal to one of characters in str
this means when searching the string "I Like C++ Tutorial" for the string "Like" the last character that apears in both strings is "i" wich is at position 16.
when searching for a complete string use std::find
std::string s("I Like C++ Tutorial");
std::cout << s.find("Like"); // prints 2
if you want to find the last occurence of the string use std::rfind
std::string s("I Like C++ Tutorial Like");
std::cout << s.rfind("Like"); // prints 20
to get the position of the last character in the last match you just have to add the length of the string:
std::string s("I Like C++ Tutorial Like");
std::string s2("Like");
std::cout << s.rfind(s2) + s2.length(); // prints 24
answered Mar 22 at 9:55
peterzugerpeterzuger
1113
std::find_last_of
Finds the last character equal to one of characters in str
this means when searching the string "I Like C++ Tutorial" for the string "Like" the last character that apears in both strings is "i" wich is at position 16.
when searching for a complete string use std::find
std::string s("I Like C++ Tutorial");
std::cout << s.find("Like"); // prints 2
if you want to find the last occurence of the string use std::rfind
std::string s("I Like C++ Tutorial Like");
std::cout << s.rfind("Like"); // prints 20
to get the position of the last character in the last match you just have to add the length of the string:
std::string s("I Like C++ Tutorial Like");
std::string s2("Like");
std::cout << s.rfind(s2) + s2.length(); // prints 24
answered Mar 22 at 9:55
peterzugerpeterzuger
1113
answered Mar 22 at 9:55
peterzugerpeterzuger
1113
answered Mar 22 at 9:55
peterzugerpeterzuger
1113
answered Mar 22 at 9:55
peterzugerpeterzuger
1113
1113
add a comment |
add a comment |
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7
read the docs to see why
find_last_ofbehaves that way, you wantrfindif you want to match a substring in a string from the end– EdChum
Mar 22 at 9:36