我的程序的要点是将数字1 - 1,000,000写入文本文件,生成一个介于1和1,000,000之间的随机数字,在文本文件中搜索该行,取其值并将其平方(这只是一个为我锻炼,它没有实际应用)。问题是,每当我运行它时,值都保持不变,但rand()
函数被time(0)
接种。我怀疑它是垃圾值,但我不知道它来自哪里(我没有使用GDB或任何其他独立调试器的经验)。下面是我的源代码:程序总是产生相同的值?
#include <fstream>
#include <ctime>
#include <iostream>
#include <string>
#include <cstdlib>
using namespace std;
int main(int argc, char** argv){
ofstream file("log.txt", ios::app);
ofstream programLog("programlog.dat", ios::app);
cout << "Test Start" << endl;
programLog << "Test Start" << endl;
cout << "Log file created" << endl;
programLog << "Log file created" << endl;
ifstream readFile("log.txt");
int foundNum;
std::string line = "";
unsigned int loopCount = 1000000;
unsigned int numToSearch;
const unsigned short min = 1;
const int max = 1000000;
unsigned int randomLine = 0;
for(int i = 0; i <= loopCount; i++){
file << i << endl;
}
//select random line
srand((unsigned)time(0));
while(!(randomLine > min) && !(randomLine < max)){
randomLine = (unsigned)rand();
programLog << randomLine;
int newlines = 0;
//size_t found;
while(getline(readFile, line)){
if(line.find("\n") != string::npos)
newlines++;
if(newlines == randomLine)
numToSearch = atoi(line.c_str());
}
}
programLog << "Random line selected" << endl;
//read line
while(std::getline(readFile,line)){
if(atoi(line.c_str()) == numToSearch){
foundNum = numToSearch;
break;
}
else
continue;
}
//square it
const unsigned int squared = foundNum*foundNum;
programLog << squared;
readFile.close(); //end read
file.close(); //end log
programLog.close(); //end programlog
return 0;
}
'file << i << endl;'Rob's rule:当你的意思是''\ n''时,千万不要说'endl'。见http://stackoverflow.com/questions/5492380/what-is-the-c-iostream-endl-fiasco/5492605#5492605 –