C中整数行的结尾 [英] The end of an integer line in C

问题描述

我必须从C语言的文本文件中读取一个未定义的矩阵，我想逐行读取它，这样每一行都是一个整数数组。但我怎么知道一行的结尾，因为我不能使用\ n作为字符？
以下是代码：

I have to read an undefined matrix from a text file in C language, and i want to read it line by line so that each line will be an integer array.But how do i know where is the end of a line, since i can't use "\n" as in for characters? Here is the code:

#include "stdafx.h"
#include "stdlib.h"
#include "stdio.h"

using namespace System;

typedef struct
{
    int *v;
    int n;
}vector;



int main(array<System::String ^> ^args)
{
    vector *a;
    FILE* f;
    int n = 15;
    int i = 0;
    int j,k;
    if ((f = fopen("C:\\Users\\Mirelaa\\Documents\\visual studio 2013\\Projects\\MatriceNedefinita\\MatriceNedefinita\\Debug\\fisier2.in", "rt")) == NULL)
    {
        printf("Fisierul nu poate fi deschis!");
        exit(1);

    };

    a = (vector *)malloc(n * sizeof(vector));

    while (!feof(f))
    {
        a[i].v = (int*)malloc(n * sizeof(int));
        a[i].n = 0;
        //citeste rand
        //citesti fiecare element din rand
        j = 0;
        while (a[i].v[j] != '\0')// wrong!!

        {
            fscanf(f, "%d", &a[i].v[j]);
            j++;
            a[i].n = a[i].n + 1;
        }
        for (k = 0 ; k < a[i].n ; k++)
        {
            printf("%d", a[i].v[j]);
            printf("\n");
        }
        i++;
        if (i == n)
        {
            n = 2 * n;
            a = (vector *)realloc(a, n * sizeof(vector));
            a[i].v = (int *)realloc(a[i].v, n * sizeof(int));
        }
    }
    return 0;
}

推荐答案

读取一行整数和保存在可变大小的数组中是一种方法。

Reading a line of integers and saving in a variable sized array is one approach.

fscanf的问题（f，％d，... 是它首先读取空格并且代码丢失了'\ n'的出现。代码需要通过其他方式查找。

The trouble with fscanf(f, "%d",... is that it first reads white-space and code loses the occurrence of '\n'. Code needs to look for it by some other means.

但是不要打包 main（）中的所有代码，而应考虑辅助函数。在C函数之后读取一个行的数字并返回 NULL on 1）内存不足，2）没有数据或转换失败而没有读取数字。否则返回 vector 。它不限于任何行长度。

But rather than pack all the code in main(), consider helper functions. Following C function reads one line of numbers and return NULL on 1) out-of-memory, 2) no data or conversion failure with no numbers read. Otherwise return vector. It is not limited to any line length.

typedef struct {
  int *v;
  size_t n;
} vector;

vector *Read_vector(vector *v1, FILE *inf) {
  v1->v = NULL;
  v1->n = 0;
  size_t size = 0;
  for (;;) {
    int number;
    int ch;
    // Check leading white-space for \n
    while (isspace(ch = fgetc(inf))) {
      if (ch == '\n') break;
    }
    if (ch == '\n' || ch == EOF) break;
    ungetc(ch, inf);
    if (1 != fscanf(inf, "%d", &number)) {
      break;
    }
    //  Is `v1` large enough?
    if (v1.n >= size) {
      size = size*2 + 1;
      vector nu;
      nu.v = realloc(v1->v, size * sizeof *nu.v);
      if (nu.v == NULL) {
        free(v1->v);
        v1->v = NULL;
        v1->n = 0;
        return NULL;
      }
      v1->v = nu.v;
    }
    v1.v[v1.n++] = number;
  }
  if (v1->n == 0) {
    return NULL;
  }
  return v1;
}

通过重复调用，可以获得一组向量。把它留给OP，因为它与上面的非常类似。

With repeated calls, an array of vectors could be had. Leave that to OP as it is very similar to the above.

注意：避免使用 while（！feof（f））。

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