如何将 C++ 字符串转换为大写
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How to Convert a C++ String to Uppercase
提问by Thomas W.
I need to convert a string in C++ to full upper case. I've been searching for a while and found one way to do it:
我需要将 C++ 中的字符串转换为全大写。我已经搜索了一段时间并找到了一种方法：
#include <iostream>
#include <algorithm>
#include <string>
using namespace std;
int main()
{
string input;
cin >> input;
transform(input.begin(), input.end(), input.begin(), toupper);
cout << input;
return 0;
}
Unfortunately this did not work and I received this error message:
不幸的是，这不起作用，我收到了以下错误消息：
no matching function for call to 'transform(std::basic_string::iterator, std::basic_string::iterator, std::basic_string::iterator,
没有匹配的函数调用 'transform(std::basic_string::iterator, std::basic_string::iterator, std::basic_string::iterator,
I've tried other methods that also did not work. This was the closest to working.
我试过其他方法也无效。这是最接近工作的。
So what I'm asking is what I am doing wrong. Maybe my syntax is bad or I need to include something. I am not sure.
所以我要问的是我做错了什么。也许我的语法不好，或者我需要包含一些东西。我不确定。
I got most of my info here: http://www.cplusplus.com/forum/beginner/75634/(last two posts)
我在这里获得了大部分信息：http: //www.cplusplus.com/forum/beginner/75634/（最后两个帖子）
回答by leemes
You need to put a double colon before toupper:
您需要在toupper:之前放一个双冒号：
transform(input.begin(), input.end(), input.begin(), ::toupper);
Explanation:
解释：
There are two different toupperfunctions:
有两种不同的toupper功能：
toupperin the global namespace (accessed with::toupper), which comes from C.toupperin thestdnamespace (accessed withstd::toupper) which has multiple overloads and thus cannot be simply referenced with a name only. You have to explicitly cast it to a specific function signature in order to be referenced, but the code for getting a function pointer looks ugly:static_cast<int (*)(int)>(&std::toupper)
toupper在::toupper来自 C的全局命名空间中（使用 访问）。toupper在具有多个重载的std命名空间（用 访问std::toupper）中，因此不能仅用名称简单地引用。您必须将其显式转换为特定的函数签名才能被引用，但是获取函数指针的代码看起来很难看：static_cast<int (*)(int)>(&std::toupper)
Since you're using namespace std, when writing toupper, 2. hides 1. and is thus chosen, according to name resolution rules.
由于您是using namespace std，因此在编写toupper时 2. 隐藏 1. 并因此根据名称解析规则被选中。
回答by Michael S Bergin
Boost string algorithms:
Boost字符串算法：
#include <boost/algorithm/string.hpp>
#include <string>
std::string str = "Hello World";
boost::to_upper(str);
std::string newstr = boost::to_upper_copy("Hello World");
回答by yizzlez
Try this small program, straight from C++ reference
试试这个小程序，直接来自C++ 参考
#include <iostream>
#include <algorithm>
#include <string>
#include <functional>
#include <cctype>
using namespace std;
int main()
{
string s;
cin >> s;
std::transform(s.begin(), s.end(), s.begin(), std::ptr_fun<int, int>(std::toupper));
cout << s;
return 0;
}
回答by jordpw
You could do:
你可以这样做：
string name = "john doe"; //or just get string from user...
for(int i = 0; i < name.size(); i++) {
name.at(i) = toupper(name.at(i));
}
回答by Joshua Fitzgerald
#include <iostream>
using namespace std;
//function for converting string to upper
string stringToUpper(string oString){
for(int i = 0; i < oString.length(); i++){
oString[i] = toupper(oString[i]);
}
return oString;
}
int main()
{
//use the function to convert string. No additional variables needed.
cout << stringToUpper("Hello world!") << endl;
return 0;
}
回答by Vishk V
You can also use the function from code below to convert it to Upper-case.
您还可以使用下面代码中的函数将其转换为大写。
#include<iostream>
#include<cstring>
using namespace std;
//Function for Converting Lower-Case to Upper-Case
void fnConvertUpper(char str[], char* des)
{
int i;
char c[1 + 1];
memset(des, 0, sizeof(des)); //memset the variable before using it.
for (i = 0; i <= strlen(str); i++) {
memset(c, 0, sizeof(c));
if (str[i] >= 97 && str[i] <= 122) {
c[0] = str[i] - 32; // here we are storing the converted value into 'c' variable, hence we are memseting it inside the for loop, so before storing a new value we are clearing the old value in 'c'.
} else {
c[0] = str[i];
}
strncat(des, &c[0], 1);
}
}
int main()
{
char str[20]; //Source Variable
char des[20]; //Destination Variable
//memset the variables before using it so as to clear any values which it contains,it can also be a junk value.
memset(str, 0, sizeof(str));
memset(des, 0, sizeof(des));
cout << "Enter the String (Enter First Name) : ";
cin >> str; //getting the value from the user and storing it into Source variable.
fnConvertUpper(str, des); //Now passing the source variable(which has Lower-Case value) along with destination variable, once the function is successfully executed the destination variable will contain the value in Upper-Case
cout << "\nThe String in Uppercase = " << des << "\n"; //now print the destination variable to check the Converted Value.
}
