從文本文件讀取2d數組而不知道邊界？

Question

所以說我正在閱讀一個文本文件的二維數組，並且我不知道尺寸是什麼，因此導致我使用malloc。這就是說，這是我的失敗嘗試，希望你們可以跟隨和指導我，因爲我很想知道如何做到這一點！

void 2dArray(double **arr, int N, int M) { 
    int i,j; 
    FILE *fp; 
    fp = fopen("array.txt", "r"); 
    for(i=0; i < N; i++) { 
    for(j=0; j < M; j++) { 
     fscanf(fp, "%lf", &arr[i][j]); 
    } 
    } 
} 

int main() { 
    int **array; 
    // How do I initialize this?? 
    // heres my attempt: 
    array = (double **)malloc(sizeof(double*); 
    2dArray(array, N, M); 
    //Where would I get N and M? 

Answer 1

首先您應該使用已知數據分配資源。爲了知道數據，你應該打開文件並計算你的二維數組的維數。它應該是這樣的：

int **array; 
int *n, *m,i; 
n = malloc(sizeof(int)); 
m = malloc(sizeof(int)); 
findArraySize(n,m); //will find and write array size to n and m 

//start of bad allocation method with lots of seperate resource in actual memory 
array = malloc(n*sizeof(double*)); //allocate resource for pointer to pointer 
for(i = 0 ; i < n ; i++) //allocate resource for each pointer 
    array[i] = malloc(m*sizeof(double)); 
//end of bad allocation method 

//or you can use the allocation method below for better performance and readability 
//(*array)[m] = malloc (sizeof(double[n][m])); 

2dArray(array, *n, *m); 

和你findArraySize功能應該是這樣的：

void findArraySize(int* n, int *m){ 
    int i,j; 
    FILE *fp; 
    char separators[] = " "; 
    char line[256]; 
    char * p; 
    *n = 0; 
    *m = 0; 

    fp = fopen("array.txt", "r"); 

    while(!eof(fp)){ 
     fgets(line, sizeof(line), fp); 
     p = strtok(line, separators); 
     *n += 1; 
     *m = 0; //we assume array is well defined, m is same for each row 
     while (p != NULL) { 
      *m += 1; 
      p = strtok(NULL, separators); 
     } 
    } 
}