C ++程序崩溃时文件读取错误

Question

I have been using this code to read integers from a file but it looks like it is crashing when being used with too many elements. The file shows in the first line how many numbers to put in the array and then the next lines have the numbers. Testing with 1000000 elements (that is my final goal) seems to crash the program.

Example input file:

8
5
6
1
4
9
3
1
2

The code:

ifstream fin;  
ofstream fout;  

fin.open("share.in", ios::in);  
fin >> days;  
int incomes[days];  
for(int i = 0; i < days; i ++){  
    fin >> incomes[i];  
    athroisma += incomes[i];  
    if(incomes[i] > minDiafora){  
        minDiafora = incomes[i];  
    }  
}  

What might be the problem and what else reading methods do you suggest using?

Answer 1

Just use a vector:

#include <vector>

//...

ifstream fin;  
ofstream fout;  

fin.open("share.in", ios::in);  
fin >> days;  
vector<int> incomes;  /***DECLARATION***/    
incomes.resize(days); /***TAKE SIZE***/

for(int i = 0; i < days; i ++){  
    fin >> incomes[i];  
    athroisma += incomes[i];  
    if(incomes[i] > minDiafora){  
        minDiafora = incomes[i];  
    }  
}

//do something...

Reference here: http://www.cplusplus.com/reference/vector/vector/

You shouldn't use static arrays for noconst-sizes :)

Answer 2

A few notes based on the code posted:

• you don't need to keep track of all the elements
• you also don't care how long the file is per se

An example of how to do what you appear to want with a forward only read:

ifstream fin;  
ofstream fout;  
int days;
int income;
int minDiafora = std::numeric_limits<int>::min();
int athroisma = 0;
fin.open("share.in", ios::in);  
fin >> days; // ignore first
while(fin >> income) // implicitly checks to see if there is anything more to read
{
    athroisma += income;
    minDiafora = std::max(minDiafora, income)
}