筆者這半年來一直是自己手動將編碼後的資料一個一個敲到excel中的，真是笨的可以，今天終於下定決心寫個小程式。

首先感謝下面的博主：

https://blog.csdn.net/sruru/article/details/7911675 告訴了我怎麼在main函式傳入引數

https://blog.csdn.net/lioncv/article/details/43151325 實現了從string中提取數字的方法

https://zhidao.baidu.com/question/560022081.html 實現了怎麼從txt檔案中讀取需要的一行

下面給出程式碼

#include<iostream>
#include<fstream>
#include<stdio.h>
#include<string>
#include<iomanip>
#include<vector>

using namespace std;

void extractFiguresFromStr2Vec(string str, vector<double> &vec);//function in which extract double numbers for string
int  countLines(const char *filename);//function in which count line numbers of a file

void main(int argc, char*argv[])
{
	//printf("%s\n", argv[1]);
	const char *filename = argv[1];

	string content, str1, str2;
	int n = countLines(filename);

	ifstream file;
	file.open(filename, ios::in);
	for (int i = 0; i < n; i++)
	{
		getline(file, content);
		if (i == n - 21)
			str1 = content;//string containing BD-rate, BD-psnr is stored in str1 for further extraction
		if (i == n - 1)
			str2 = content;//string containing coding time is stored in str2 for further extraction
	}
	file.clear();
	file.close();

    vector<double> vec1;//vector containing BD-rate, BD-psnr data
	vector<double> vec2;//vector containing coding time
	extractFiguresFromStr2Vec(str1, vec1);
	extractFiguresFromStr2Vec(str2, vec2);
	cout << vec1[1] << "\t" << vec1[2] << "\t" << vec1[3] << "\t" << vec1[4] << "\t" << vec2[0] << endl;
}

void extractFiguresFromStr2Vec(string str, vector<double> &vec){
	const char *s = str.c_str();
	const char *pstr;
	int i = 0, j = 0;
	int k;
	int ndigit = 0;
	pstr = &s[0];

	for (i = 0; *(pstr + i) != '\0'; i++){
		if ((*(pstr + i) >= '0') && (*(pstr + i) <= '9') || *(pstr + i) == '.')
			j++;
		else{
			if (j > 0){
				string str;
				for (k = j; k > 1; k--){
					str.append(pstr + i - k);
				}
				vec.push_back(atof(str.c_str()));
				ndigit++;
				j = 0;
			}
		}
	}
	if (j > 0){
		string str;
		for (k = j; k > 1; k--){
			str.append(pstr + i - k);
		}
		vec.push_back(atof(str.c_str()));
		ndigit++;
		j = 0;
	}
}

int countLines(const char *filename)
{
	int n = 0;
	string temp;

	ifstream file;
	file.open(filename, ios::in);
	if (file.fail())
	{
		printf("open file \"%s\" error\n", filename);
		exit(2);
	}
	else
	{
		while (getline(file, temp))
		{
			n++;
		}
		return n;
	}
	file.close();
}