它在字符串搜索与参数中指定的任何字符都不匹配的第一个字符。在这里，我们将描述其拥有的所有语法。
返回值：成功时第一个不匹配字符的索引；如果找不到这样的字符，则返回字符串:: npos。
语法1：搜索不是字符串str元素的第一个字符。
size_type string::find_first_not_of (const string& str) const
str : Another string with the set of characters
to be used in the search.
// CPP code for find_first_not_of (const string& str) const
#include
using namespace std;
// Function to demonstrate find_first_not_of
void find_first_not_ofDemo(string str1, string str2)
{
// Finds first character in str1 which
// is not present in str2
string::size_type ch = str1.find_first_not_of(str2);
cout << "First unmatched character : ";
cout << str1[ch];
}
// Driver code
int main()
{
string str1("Hello World!");
string str2("GeeksforGeeks");
cout << "Original String : " << str1 << endl;
cout << "String to be looked in : " << str2 << endl;
find_first_not_ofDemo(str1, str2);
return 0;
}
输出：
Original String : Hello World!
String to be looked in : GeeksforGeeks
First unmatched character : H
语法2：搜索从索引IDX的第一个字符不是字符串str的元件。
size_type string::find_first_not_of (const string& str, size_type idx) const
str : Another string with the set of characters
to be used in the search.
idx : is the index number from where we have to
start finding first unmatched character.
// CPP code for string::find_first_not_of
// (const string& str, size_type idx) const
#include
using namespace std;
// Function to demonstrate find_first_not_of
void find_first_not_ofDemo(string str1, string str2)
{
// Finds first character in str1 from index 3 which
// is not present in str2
string::size_type ch = str1.find_first_not_of(str2, 3);
cout << "First unmatched character : ";
cout << str1[ch];
}
// Driver code
int main()
{
string str1("geeKsforgeeks");
string str2("GeeksforGeeks");
cout << "Original String : " << str1 << endl;
cout << "String to be looked in : " << str2 << endl;
find_first_not_ofDemo(str1, str2);
return 0;
}
输出：
Original String : geeKsforgeeks
String to be looked in : GeeksforGeeks
First unmatched character : K
语法3：搜索是或不是也是C-串CSTR的元件的第一个字符。
size_type string::find_first_not_of (const char* cstr) const
cstr : Another C-string with the set of characters
to be used in the search.
请注意，cstr可能不是空指针(NULL)。
// CPP code for string::find_first_not_of (const char* cstr) const
#include
using namespace std;
// Function to demonstrate find_first_not_of
void find_first_not_ofDemo(string str)
{
// Finds first character in str which
// is not present in "geeksforgeeks"
string::size_type ch = str.find_first_not_of("geeksforgeeks");
cout << "First unmatched character : ";
cout << str[ch];
}
// Driver code
int main()
{
string str("GeeksforGeeks");
cout << "Original String : " << str << endl;
find_first_not_ofDemo(str);
return 0;
}
输出：
Original String : GeeksforGeeks
First unmatched character : G
语法4：搜索从索引IDX的第一个字符不属于C-串CSTR的元件
size_type string:: find_first_not_of (const char* cstr, size_type idx) const
cstr : Another string with the set of characters
to be used in the search.
idx : is the index number from where we have to
start finding first unmatched character.
请注意，cstr可能不是空指针(NULL)。
// CPP code for size_type string:: find_first_not_of
// (const char* cstr, size_type idx) const
#include
using namespace std;
// Function to demonstrate find_first_not_of
void find_first_not_ofDemo(string str)
{
// Finds first character in str from 5th index which
// is not present in "geeksforgeeks"
string::size_type ch = str.find_first_not_of("geeksForgeeks", 5);
cout << "First unmatched character : ";
cout << str[ch];
}
// Driver code
int main()
{
string str("GeeksforGeeks");
cout << "Original String : " << str << endl;
find_first_not_ofDemo(str);
return 0;
}
输出：
Original String : GeeksforGeeks
First unmatched character : f
语法5：查找str中不等于char c的第一个字符。
size_type string::find_first_not_of (char c) const
c Character c with which contents of str are required to be compared.
// CPP code for size_type string:: find_first_not_of (char c) const
#include
using namespace std;
// Function to demonstrate find_first_not_of
void find_first_not_ofDemo(string str)
{
// Finds first character in str which
// is not equal to character 'G'
string::size_type ch = str.find_first_not_of('G');
cout << "First unmatched character : ";
cout << str[ch];
}
// Driver code
int main()
{
string str("GeeksforGeeks");
cout << "Original String : " << str << endl;
find_first_not_ofDemo(str);
return 0;
}
输出：
Original String : GeeksforGeeks
First unmatched character : e
语法6：从索引idx查找str中的第一个字符，该字符不等于char c。
size_type string::find_first_not_of (char c, size_type idx) const
c : Character c with which contents of str
are required to be compared.
idx : index from where search of the first
unmatched character is to be started
// CPP code for size_type string::find_first_not_of
// (char c, size_type idx) const
#include
using namespace std;
// Function to demonstrate find_first_not_of
void find_first_not_ofDemo(string str)
{
// Finds first character in str from 6th index which
// is not equal to character 'G'
string::size_type ch = str.find_first_not_of('G', 6);
cout << "First unmatched character : ";
cout << str[ch];
}
// Driver code
int main()
{
string str("GeeksforGeeks");
cout << "Original String : " << str << endl;
find_first_not_ofDemo(str);
return 0;
}
输出：
Original String : GeeksforGeeks
First unmatched character : o
语法7：搜索也没有字符数组字符的字符chars_len的元件，开始于索引IDX的第一个字符。
size_type string::find_first_not_of
(const char* chars, size_type idx, size_type chars_len) const
*chars : is the character array with which
searching of first unmatched is to be performed.
idx : index number in string
chars_len : is the character length in
*chars to be picked for searching purpose
// CPP code for size_type string::find_first_not_of
// (const char* chars, size_type idx, size_type chars_len) const
#include
using namespace std;
// Function to demonstrate find_first_not_of
void find_first_not_ofDemo(string str)
{
// Finds first character in str from 4th index which
// is not equal to any of the first 3 characters from "svmnist"
string::size_type ch = str.find_first_not_of("svmnist", 4, 3);
cout << "First unmatched character : ";
cout << str[ch];
}
// Driver code
int main()
{
string str("GeeksforGeeks");
cout << "Original String : " << str << endl;
find_first_not_ofDemo(str);
return 0;
}
输出：
Original String : GeeksforGeeks
First unmatched character : f
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