如何检查将在数组中放入多少个值 [英] How to check how many values will be put in an array
问题描述
给出一个大小为N的数组，C程序将读取一个文本文件，其中包含由空格分隔的数字，并将它们存储到数组中。 N编号是文件中的第一个，与其他编号位于不同的行中。
txt文件示例：
Giving an array with size of N the C program will read a text file that contain numbers separeted by whitespace and will store them into the array. The N number is the first one in the file and is in different line than the other numbers.
Example of txt file:
10
9 8 5 4 585 2 14 5 9 8
我想检查数组保存的确切时间数字，如果有更多的数字比数组的实际大小（例如12个数字）退出。
我搜索所有网络以找到解决方案，但我不能。
我创建了一个用fscanf读取文件的代码，但是如果读取超过200.000个元素，它会减慢程序的速度。
以下是代码：
I want to make a check the exact time the array will save the number, if there are more numbers than the actual size of the array (eg 12 numbers) to exit.
I search all the web to find a solution but I couldn't.
I created a code that read the file with fscanf, but it slow down the program if should read more than 200.000 elements.
Here's the code anyway :
File *stream
stream = fopen("xxx_big.txt", "r");
int t_size;
fscanf(stream, "%d", &t_size);
int num = 0;
int value = 0;
while ( fscanf ( stream, "%d", &value) == 1)
{
num++;
}
if ( num > t_size)
{
printf ( "too many integers\n");
getchar();
return 1;
}
if ( num < t_size)
{
printf ( "not enough integers\n");
getchar();
return 1;
}
fclose(stream);
我的程序使用getline（）来读取和将数字拆分成一个字符然后使用以下代码将数字保存到数组中：
My program use getline() to read and split the numbers into a char and then using the following code will save the numbers into the array:
count = atoi(lines[0]); // First row has count
my_array = (int*)malloc(count * sizeof(int));
if (my_array==NULL) {
printf("Error allocating memory!\n"); //print an error message
return 1; //return with failure
getchar();
}
for (i = 0; i < count; ++i) {
my_array[i] = atoi(lines[i + 1]);
}
但正如我所提到的，我已经将数字放入char中，因此检查应该很容易创建。
这里是所有代码（没有fscanf检查）：
But as I mentioned I already put the numbers into a char so that check should be easy enough to create.
Here's all the code (without the fscanf check):
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
int is_end(char* input) {
return *input == 0;
}
int is_linebreak(char* input) {
return *input == '\r' || *input == '\n' || *input == ' ';
}
char* eat_linebreaks(char* input) {
while (is_linebreak(input))
++input;
return input;
}
size_t count_lines(char* input) {
char* p = input;
size_t rows = 1;
if (is_end(p))
return 0;
while (!is_end(p)) {
if (is_linebreak(p)) {
++rows;
p = eat_linebreaks(p);
}
else {
++p;
}
}
return rows;
}
/* split string by lines */
char** get_lines(char* input, size_t line_count) {
char* p = input;
char* from = input;
size_t length = 0;
size_t line = 0;
int i;
char** lines = (char**)malloc(line_count * sizeof(char*));
do {
if (is_end(p) || is_linebreak(p)) {
lines[line] = (char*)malloc(length + 1);
for (i = 0; i < length; ++i)
lines[line][i] = *(from + i);
lines[line][length] = 0;
length = 0;
++line;
p = eat_linebreaks(p);
from = p;
}
else {
++length;
++p;
}
} while (!is_end(p));
// Copy the last line as well in case the input doesn't end in line-break
lines[line] = (char*)malloc(length + 1);
for (i = 0; i < length; ++i)
lines[line][i] = *(from + i);
lines[line][length] = 0;
++line;
return lines;
}
int main(int argc, char* argv[]) {
char** lines;
size_t size;
size_t number_of_rows;
int count;
int* my_array;
FILE *stream;
char *contents;
int fileSize = 0;
int i;
// Open file, find the size of it
stream = fopen("xxx.txt", "r");
if (stream == NULL)
{
printf("Opening 'xxx.txt' file failed: %s\n",strerror(errno));
getchar();
return 0;
}
else {
fseek(stream, 0L, SEEK_END);
fileSize = ftell(stream);
fseek(stream, 0L, SEEK_SET);
// Allocate space for the entire file content
contents = (char*)malloc(fileSize + 1);
// Stream file into memory
size = fread(contents, 1, fileSize, stream);
contents[size] = 0;
fclose(stream);
// Count rows in content
number_of_rows = count_lines(contents);
// Get array of char*, one for each line
lines = get_lines(contents, number_of_rows);
// Get the numbers out of the lines
count = atoi(lines[0]); // First row has count
my_array = (int*)malloc(count * sizeof(int));
if (my_array==NULL) {
printf("Error allocating memory!\n"); //print an error message
return 1; //return with failure
getchar();
}
for (i = 0; i < count; ++i) {
my_array[i] = atoi(lines[i + 1]);
}
printf("All up and running! Array created! :D \n\n Array values: \n");
for(i = 0; i < count; i++ )
{
printf(" %d : %d\n", i, my_array[i]);
}
free(my_array);
fclose(stream);
return 0;
}
}
推荐答案
这是这个问题的最新重复，似乎没有去过任何地方。有人不止一次建议你先将整个文件读入内存，然后再加快处理。使用令牌拆分功能之一[ ^ ]获取第一个数字，然后列出所有其他数字。这允许您迭代数字，一次计数，然后第二次将它们转换为整数并将它们保存在数组中。
This is the latest repeat of this question and does not seem to be going anywhere. It has been suggested more than once that you read the entire file into memory first and then you can process it much faster. Use one of the token splitting functions[^] to get the first number, and then all others in the list. This allows you to iterate over the numbers, once to count them, and then a second time to convert them to integers and save them in the array.
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