C++读取txt文件时，读取前几列的问题

Question

C++中使用ifstream读取txt文件，txt文件如上图，前三列是坐标信息，最后一列没有价值；怎样只读取前三列，跳过第四列？

Answer 1

#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main(){
	ifstream in("D://1.txt");
	char str[1000];

	int icount = 0;
	while (in.getline(str, 1000))
	{
		std::string test = str;
		string a = test.substr(0, test.find_first_of(" "));
		test = test.substr(test.find_first_of(" ") + 1, test.length());
		string b = test.substr(0, test.find_first_of(" "));
		test = test.substr(test.find_first_of(" ") + 1, test.length());
		string c = test.substr(0, test.find_first_of(" "));
		test = test.substr(test.find_first_of(" ") + 1, test.length());
		cout << a<<b<<c << endl;

	}
}