C stringstream在类型转换中的应用

概述

在C++中， 定义了三个类：istringstream、ostringstream 和 stringstream，分别用来进行流的输入、输出和输入输出操作。

应用

笔者在解答力扣第8题字符串转换整数 (atoi)时便采用了这一方法进行解答。

class Solution {
public:
    int myAtoi(string str) {
        stringstream sstream;
        int ret = 0;
        sstream << str;
        sstream >> ret;
        return ret;
    }
};

or

class Solution {
public:
    int myAtoi(string s) {
        if(s == "")
            return 0;
        stringstream ss(s);
        int ret = 0;
        ss >> ret;
        return ret;
    }
};

当然在实际变成时，我们还是尽量使用系统自带的标准库吧

// Convert string to digit
#include <iostream>
#include <string>
int main()
{
    std::string s = "10";
    //use stoi convert string to digit
    int i = std::stoi(s);
}

string append VS stringstream

如果仅是进行字符串的拼接则最好使用append或者operator+，但是如果想在拼接的过程中，顺便完成数据格式的转换后再拼接，则使用stringstream。

I don’t know which one will be faster, but if I had to guess I’d say your second example is, especially since you’ve called the reserve member function to allocate a large space for expansion. If you’re only concatenating strings use string::append (or string::operator+=).

If you’re going to convert numbers to their string representation, as well as format them during conversion, and then append the conversion results together, use stringstreams. I mention the formatting part explicitly because if you do not require formatting C++11 offers std::to_string which can be used to convert numeric types to strings.