字符串大小写转换

#include<iostream>
#include<string>

using namespace std;

void upper_string(const char* input, char* out)
{
    unsigned int len = strlen(input);
    for (unsigned int i=0; i<len; i++)
    {
        out[i]=(char)toupper(input[i]);
    }
    out[len]='\0';
}

void lower_string(const char* input, char* out)
{
    unsigned int len = strlen(input);
    for (unsigned int i=0; i<len; i++)
    {
        out[i]=(char)tolower(input[i]);
    }
    out[len]='\0';
}

int main()
{
    char* astring = "Hello World";
    char result[20];
    lower_string(astring,result);
    cout<<result<<endl;
    upper_string(astring,result);
    cout<<result<<endl;
    return 0;
}