我正在尝试为康威的C生命游戏编写代码。我对包含我的宇宙的2D数组有一些问题。我将向您展示一些导致我出现问题的代码。实际上我有两个问题无法处理。
#include <stdio.h>
#include <stdlib.h>
#include "file2ppm.h"
typedef enum { false, true } bool;
void *allocateMemoryFor2DArray(int x, int y); //allocate memory for 2D array
void initializeUniverseFromFile(char* path, int x, int y, int array[x][y]); //set values of cells from a file
void initializeUniverseRandomly(int x, int y, int array[x][y]); //set random values
int getNumberOfColumns (FILE *file); //get number of columns in file (yDim of Universe)
int getNumberOfLines (FILE *file); //get number of lines in file (xDim of Universe)
void print2DArray (int x, int y, int array[x][y]); //print 2D array
void setDimensionsFromFile(char* path,int* xDim, int* yDim, int* xDimB, int* yDimB);//set dimensions of Universe
int main(int argc, char * argv[])
{
int i, j, n; //loop indexes
int nsteps; //Number of generations
int im, ip, jm, jp; //neighbour boundaries
int yDim, xDim; //Universe boundarier defined by user (Living area);
int xDimB, yDimB; //Universe boundaries expanded to each side by 1
int nsum, isum; //sum of neighbours, sum of alive cells after iteration
//int **old, **new; //Universe
int (*old)[xDimB]; //Universe
int (*new)[xDimB]; //Universe
float x; //to randomize first population
char *inputPath; //Path to file with ixDimBtial uxDimBverse
char *outputPath; //Path to output ppm files
//temporary copy
int yDim_copy, xDim_copy;
printf("argc: %d\n", argc);
switch (argc){
case 4: //Read the initial Universe from file
//Take arguments
nsteps = atoi(argv[1]); //Get number of iterations
outputPath = argv[2]; //Get path for outputimages
inputPath = argv[3]; //File with initialize uxDimBverse;
setDimensionsFromFile(inputPath, &xDim, &yDim, &xDimB, &yDimB);
old = allocateMemoryFor2DArray(xDimB, yDimB); //Alocate memory for expanded Universes
new = allocateMemoryFor2DArray(xDimB, yDimB);
printf("Before initialize: yDim: %d, xDim: %d\n", yDim, xDim); //Here the values are good
//tmp copy
yDim_copy = yDim;
xDim_copy = xDim;
initializeUniverseFromFile(inputPath, xDim, yDim, old);
printf("After initialize: yDim: %d, xDim: %d\n", yDim, xDim); //And here one dim is changed
yDim = yDim_copy; //I took a copy to avoid this problem for now
xDim = xDim_copy;
printf("After taking from copy: yDim: %d, xDim: %d\n", yDim, xDim);//Here dimensions are good again
memcpy (new, old, xDimB*yDimB*sizeof(old[xDimB][yDimB])); //Copy old to new
break;
default:
printf("Usage: %s iter_number, output_name, yDim, xDim\n", argv[0]);
printf("or\n");
printf("Usage: %s iter_number, output_name, ixDimBtial_input_name\n", argv[0]);
printf("Note: Initial file have to be in ./data/\n");
return 1;
}
print2DArray(xDim, yDim, old); //this works fine
printf("In main: yDim: %d, xDim: %d\n", yDim, xDim);
printf("%d\n", old[0][0]); //this works fine
printf("%d\n", old[2][2]); //Segmentation failure
return 0;
}
void *allocateMemoryFor2DArray(int x, int y){
int (*array)[y] = malloc( sizeof(int[x][y]) ); //Allocate memory
if (array == NULL) { /* always check the return of malloc */
perror("malloc");
exit(EXIT_FAILURE);
}
return array;
}
int getNumberOfColumns (FILE *file){
int yDim = 0;
char ch;
do
{
ch = getc(file); //Get 1 char from file
if (ch == '\n') //If ch is new line
{
rewind(file); //Move file pointer to beginxDimBng of file
return yDim; //Found number of columns
}
else
++yDim;
}while (ch != EOF);
}
int getNumberOfLines (FILE *file){
int xDim = 0;
char ch;
do
{
ch = getc(file); //Get 1 char from file
if(ch == '\n') //If new line
{
++xDim; //Increase xDim (another row)
}
}while(ch != EOF);
rewind(file); //Move file pointer to beginxDimBng of file
return xDim;
}
void print2DArray (int x, int y, int array[x][y])
{
int i, j;
printf("x: %d, y: %d\n", x, y);
for (i = 1; i <= x; ++i)
{
for (j = 1; j <= y; ++j)
{
printf("%d ", array[i][j]);
}
printf("\n");
}
}
void setDimensionsFromFile(char* path, int* xDim, int* yDim, int* xDimB, int* yDimB)
{
FILE *file;
int i,j;
file = fopen(path, "r"); //open file
if (file)
{
*yDim = getNumberOfColumns (file);
*xDim = getNumberOfLines (file);
*xDimB = *xDim + 2; // add 2 for left and right torus topology
*yDimB = *yDim + 2;
if (*xDim > 0 && *yDim > 0)
{
printf("UxDimBverse dimension %d x %d\n", *xDim , *yDim);
}
else
{
perror("Wrong initialize file");
exit(EXIT_FAILURE);
}
fclose(file); //Close file
}
else
{
perror("Open initialize file error");
exit(EXIT_FAILURE);
}
}
void initializeUniverseFromFile(char* path, int x, int y, int array[x][y])
{
FILE *file;
int i,j;
file = fopen(path, "r"); //open file
if (file)
{
//IxDimBtialize array
char *ch;
for (i = 1; i <= x; i++)
{
//printf("i: %d ", i);
for (j = 1; j <= y; j++)
{
//printf("j: %d ", j);
if (fscanf(file, "%c", ch) != 1)
{
perror("Read error\n");
}
else if (isdigit((unsigned char)*ch))
{
printf("%d", atoi(ch));
array[i][j] = atoi(ch);
}
else
{
//printf("Numer znaku: %d ", ch);
j--;
}
}
printf("\n");
}
printf("Done reading\n");
fclose(file); //Close file
}
else
{ //File open error
perror("Open initialize file error");
exit (EXIT_FAILURE);
}
printf("In initialize yDim: %d, xDim: %d\n", x, y);
}
void initializeUniverseRandomly(int x, int y, int array[x][y])
{
int i, j;
float r;
for (i = 1; i <= x; i++) {
for (j = 1; j <= y; j++) {
r = rand() / ((float)RAND_MAX + 1);
if (r<0.5) {
array[i][j] = i*x+j;
}
else {
array[i][j] = i*x+j;
}
}
}
}
问题1：
我设置了宇宙的维度（变量xDim和yDim）。我在第45行打印它们（检查注释//这里的值很好）。然后我打电话给initializeUniverseFromFile(inputPath, xDim, yDim, old);
其中一个维度值已更改。我不知道为什么。这就是为什么我临时复制这些变量的原因，因为我花了2个小时寻找这个错误。我甚至在initializeUniverseFromFile函数的末尾打印出这些变量，它们没问题。但是当我再次回到主（第50行）时，价值会发生变化。这是一个小问题。更糟糕的是：
问题2 我有一个指针 int（* old）[xDimB];
xDimB是xDim + 2所以它总是大于xDim
我用函数初始化数组
allocateMemoryFor2DArray(xDimB, yDimB)
然后我这样做：
print2DArray(xDim, yDim, old); //this works fine
printf("In main: yDim: %d, xDim: %d\n", yDim, xDim); //Dimensions are fine
printf("%d\n", old[0][0]); //this works fine
for (i=0; i<=xDim; ++i)
printf("%d ", old[0][i]; //this works fine too
printf("%d\n", old[2][2]); //Segmentation failure
打印整个数组功能很好 从第一行打印值很好 从数组中间打印值会产生错误。
答案 0 :(得分：2)
我设置了宇宙的维度（变量xDim和yDim）
在声明VLA int (*old)[xDimB];和int (*new)[xDimB];之前，您需要包含有效数字。当xDim和yDim具有已知的已验证值时，将这些VLA声明移至计划的后一点。
答案 1 :(得分：-2)
我无法在代码中解释两件可能导致分段错误的原因。
1）
void *allocateMemoryFor2DArray(int x, int y);
当您明确返回整数数组时，为什么它无效。
2）如何在单个指针上返回2D数组？ 要定义2D数组，您需要一个双指针：
int** array = new int*[x];
然后循环遍历x以定义第二个维度：
for (int i=0;i<x;i++)
array[i] = new int[y];
你终于返回双指针，它是对你数组的引用。
你的功能会变成这样：
int** allocateMemoryFor2DArray(int x, int y)
{
int** array = new int*[x];
for (int i=0;i<x;i++)
array[i] = new int[y];
return array;
}
同样这些功能：
void initializeUniverseFromFile(char* path, int x, int y, int array[x][y])
void initializeUniverseRandomly(int x, int y, int array[x][y])
void print2DArray (int x, int y, int array[x][y])
应该成为：
void initializeUniverseFromFile(char* path, int x, int y, int** array)
void initializeUniverseRandomly(int x, int y, int** array)
void print2DArray (int x, int y, int** array)
最后你在main中的指针也应该成为双指针。
第一行打印而其他行不打印的原因是您没有循环抛出第一个维度以在第二维中初始化该数组。