C++从文件输入数据

input.txt文件内容

8
1.0 0.9973978 0.9896158 0.9767267 0.9588510 0.9361556 0.9088516 0.8771925 0.8414709

方案一

#include
#include
using namespace std;
ifstream fi("input.txt", ios::in);
int main()
{
	int n;
	fi >> n;
	double* arr = new double[n + 1];
	cout << n << endl;
	for (int i = 0; i <= n; i++) {
		fi >> arr[i];
	}
	for (int i = 0; i <= n; i++) {
		cout << arr[i] << "  ";
	}
	cout << endl;
	delete[] arr;
	system("pause");
	return 0;
}

运行结果：

方案二：

#include
#include
using namespace std;
fstream fi("input.txt", ios::in);
fstream fo("output.txt", ios::out | ios::trunc);
int main()
{
	cin.rdbuf(fi.rdbuf());
	cout.rdbuf(fo.rdbuf());
        return 0;
}