Question

C++怎么读取txt文件并且统计里面的数字：求详解

老师给的作业是打开一个random.txt：
100
200
300
400
500
600
700
用c++统计这个txt中有几个数字（7个），并且计算总和和平均值
我写的程序：#include <fstream>
using namespace std;

int main()
{
ifstream inputFile;
string filename = "random.txt";
int number=0;
//number of numbers
int numbers,sum,average;

// Open the file.
inputFile.open(filename.c_str());

// If the file successfully opened, process it.
if (inputFile)
{

while (inputFile >> numbers)
{
inputFile >> numbers;
number++;
sum=sum+numbers;

}
average = sum / number;
//get average and display all:
cout << "number of numbers: "<<number<<"\n";
cout << "sum of numbers : "<<sum<<"\n";
cout << "average of numbers: "<< average<<"\n";
}
else
{
// Display an error message.
cout << "Error opening the file.\n";
}

system("pause");
return 0;
}
可以调试和生成exe，但是运行出来结果是这样的：





Answer 1

1.C语言读取TXT文件的行数并把把TXT文件的内容存到数组中，需要根据每行的内容（字符，数字，字符串）选取fgets、fscanf或者fgets。
这里假设每行是一个字符串，每行不超过127个字符（用数组存字符串，最后一位存'\0'），选取fgets进行读取。


2.示例代码如下：

#include <stdio.h>
#include <stdlib.h>
int main(int argc, char* argv) {
    FILE* rf = fopen("input.txt","r");
    char a[1024][128];
    int i=0;
    while(fgets(a[i],128,rf))i++;
    int n=i; 
    printf("行数：%d\n",n);
    fclose(rf);
    i=0;
    while(i<n)printf("%s",a[i++]);
    system("pause");
    return 0;
}

Answer 2

sum 没有初始化。

#include <fstream>
using namespace std;

int main()
{
ifstream inputFile;
string filename = "random.txt";
int number=0;
//number of numbers
int numbers,average;
int sum=0; //sum要初始化，否则是个不可预料的值

// Open the file.
inputFile.open(filename.c_str());

// If the file successfully opened, process it.
if (inputFile)
{

while (inputFile >> numbers)
{
inputFile >> numbers;
number++;
sum=sum+numbers;

}
average = sum / number;
//get average and display all:
cout << "number of numbers: "<<number<<"\n";
cout << "sum of numbers : "<<sum<<"\n";
cout << "average of numbers: "<< average<<"\n";
}
else
{
// Display an error message.
cout << "Error opening the file.\n";
}

system("pause");
return 0;
}