从字符串中移除前3个字符

感谢 Lincoln 在下面的评论，我改变了这个答案。

删除字符串前3个字符的最有效方法是什么？

例如:

'apple' change to 'le'
'a cat' change to 'at'
' a b c'change to 'b c'
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小开
最佳答案

下面的答案在编译时正确处理8位 int。但是，它确实需要 C + + 17。如果你没有 C + + 17，你将不得不做一些其他的事情(例如，提供这个函数的重载，一个用于 uint8 _ t，一个用于 int8 _ t，或者使用一些除了“ If conexpr”之外的东西，也许可以启用 _ If)。

template< typename T >
std::string int_to_hex( T i )
{
// Ensure this function is called with a template parameter that makes sense. Note: static_assert is only available in C++11 and higher.
static_assert(std::is_integral<T>::value, "Template argument 'T' must be a fundamental integer type (e.g. int, short, etc..).");


std::stringstream stream;
stream << "0x" << std::setfill ('0') << std::setw(sizeof(T)*2) << std::hex;


// If T is an 8-bit integer type (e.g. uint8_t or int8_t) it will be
// treated as an ASCII code, giving the wrong result. So we use C++17's
// "if constexpr" to have the compiler decides at compile-time if it's
// converting an 8-bit int or not.
if constexpr (std::is_same_v<std::uint8_t, T>)
{
// Unsigned 8-bit unsigned int type. Cast to int (thanks Lincoln) to
// avoid ASCII code interpretation of the int. The number of hex digits
// in the  returned string will still be two, which is correct for 8 bits,
// because of the 'sizeof(T)' above.
stream << static_cast<int>(i);
}
else if (std::is_same_v<std::int8_t, T>)
{
// For 8-bit signed int, same as above, except we must first cast to unsigned
// int, because values above 127d (0x7f) in the int will cause further issues.
// if we cast directly to int.
stream << static_cast<int>(static_cast<uint8_t>(i));
}
else
{
// No cast needed for ints wider than 8 bits.
stream << i;
}


return stream.str();
}

只需使用子字符串: "apple".substring(3);将返回 le

小开

原来的答案并不像我想的那样正确处理8位整数:

使用 绳子类的 子串方法:

String removeCurrency=amount.getText().toString().substring(3);

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