Question

有人可以在此代码中找到我的错误吗？我必须从命令行中读取这个课程注册文件，该文件具有不同学生ID的类名和优先级（ClassName StudentID Priority，每行），并输出三个文件（每个类）按顺序包含谁先入住。我不允许看到优先级队列类，但int是该学生的优先级。另外，我需要三个输出文件的三个流吗？

// Course Enrollment
#include <string>
#include <fstream>
#include "p2priorityqueue.h"
#include <iostream>
using namespace std;

int main(int argc, char* argv[]){

// Declare filename string, check if there are actually arguments, pass argv[1] (the file used
// during compilation) to filename variable;
string filename; 
if(argc > 0){ 
filename = argv[1];
} 

// Declare the three variables we will use for passing data to our priority queues. 
string classN;
string userID;
int userYear;

// Declare three Priority Queues for each CS class, each with a string for the student ID and int for
// priority.
PriorityQueue<string, int> pq352;
PriorityQueue<string, int> pq365;
PriorityQueue<string, int> pq332;

// Initialize the three Priority Queues as instructed
initialize(pq352);
initialize(pq365);
initialize(pq332);
// Create input file stream called "input", and three output streams for each class
ifstream input;
ofstream output1;
ofstream output2;
ofstream output3;

// Open the file passed at compilation 
input.open(filename.c_str());


// While loop that runs until file input stream is empty. The first word is 
passed to classN,
// the second is passed to userID, and the third to userYear. We then check 
what PQ that line should belong
// to by comparing classN to CS352, CS365, CS332.
while(!input.eof()){
    input >> classN >> userID >> userYear; 
    if(classN == "CS352"){
        push(pq352, userID, userYear);
    } 
    if(classN == "CS365"){
        push(pq365, userID, userYear);
    } 
    if(classN == "CS332"){
        push(pq332, userID, userYear);
    }
}
// close the file input stream. 
input.close();



output1.open("CS352");
while(!isEmpty(pq352)){
    output1 << pop(pq352);
    output1 << endl;
}
output1.close();

output2.open("CS365");
while(!isEmpty(pq365)){
    output2 << pop(pq365);
    output2 << endl;
}
output2.close();


output3.open("CS332");
while(!isEmpty(pq332)){
    output3 << pop(pq332);
    output3 << endl;
}
output3.close();

destroy(pq352);
destroy(pq365);
destroy(pq332);
}

Answer 1

首先尝试初始化所有变量以消除任何未初始化的异常。

看起来你正试图改变未经初始化的变量。

即：

string classN = "";
string userID = "";
int userYear = -1;

这些可以保持这样：

ifstream input;
ofstream output1;
ofstream output2;
ofstream output3;

您还需要防范未初始化的文件名：

string filename; 
if(argc > 0){ 
    filename = argv[1];
} else {
    filename = "somefilename.txt"
}

否则像input.open(filename.c_str());这样会失败，因为文件名未初始化。

分段故障（核心转储） - 从命令行读取文件

1 个答案: