如何让我的程序更灵活？

问题描述

您好。我用C制作了一个程序，我完成了它。我的问题如下。

我读了一个包含1.000.000个数字的 xxx.in 文件，并使用scanf将它们存储在动态数组中。另外我首先读取文件中的第一个数字，该文件包含1.000.001个数字，命令为 fscanf（fp，％d，& t_size）; 只知道，我们想要创建一个大小为1.000.000的数组。然后我用以下代码存储值：

Hello. I made a program in C and I'm finish it. My problem is the following though.
I read a xxx.in file that contains 1.000.000 numbers and store them in an dynamic array using scanf. Also I first read the first number in the file, with that number the file contain 1.000.001 nums, with the command "fscanf(fp, "%d", &t_size);" to know, just for case, that we want to create an array with size of 1.000.000. Then I store the values with the below code:

int i =0;
for ( i = 0; i < t_size; i++ )
{
fscanf(fp, "%d",&my_array[i]);
} 

我的问题不在于编码是我程序的灵活性。我希望从一开始到值存储的过程为1秒，而fscanf不会发生这种情况。



有人能告诉我，如果我们可以在1秒钟内使用动态阵列存储这么多的nums（使用fread或fets），我该如何制作呢？

My problem isn't the coding is the flexibility of my program. I want the procedure from the beginning through the store of values to be 1s and this can't happen with fscanf.

Can someone tell me if we can store so many nums in an dynamic array in 1 second (using fread or fets) and how can i make it?

推荐答案

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <time.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[]) {
	clock_t start;
	unsigned long microseconds;
	float seconds;
	char** lines;
	size_t size;
	size_t number_of_rows;
	int count;
	int* my_array;
	start = clock();

	FILE *stream;
	char *contents;
	int fileSize = 0;
        int i;

	// Open file, find the size of it
	stream = fopen(argv[1], "rb");
	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));
	for (i = 0; i < count; ++i) {
		my_array[i] = atoi(lines[i + 1]);
	}

	microseconds = clock() - start;
	seconds = microseconds / 1000000.0f;
	printf("Took %fs", seconds);


	return 0;
}

希望这有帮助，

Fredrik

Hope this helps,
Fredrik

这篇关于如何让我的程序更灵活？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！