你不知道的stringstream的用法

• 保留两位小数并保存到字符串
• stringstream和iostream的用法很相似

#include <sstream>
#include <iomanip>
#include <iostream>

using namespace std;

int main(int argc, char **argv) {
    
  double a = 0.13567;
  stringstream ss;
  ss << fixed << setprecision(2) << a;
  ss >> a;  //保存到double
  cout << ss.str() << endl;  //0.14

  return 0;
}

• 自己实现保留两位小数并保存到字符串
• 注意：+=比+快

string KeepTwo(double a) {
    
  int b = a * 100 + 0.5;
  string s;
  s += to_string(b/100) + ".";
  b %= 100;
  if( b  < 10) {
    
    s += "0";
  }
  s += to_string(b);

  return s;
}