更新：想出来......错误代码底部的更新代码确实如此。 谢谢你们
我试图将input.txt文件中的行读入三个矩阵，一个用于名字，一个用于姓氏，一个用于成绩。
等级矩阵很好，我无法弄清楚名称矩阵。
跑步时我得到输出：
Row 1, column 1 of grades: 1.30
Row 1, column 1 of first: P
Row 1, column 1 of last: V
字符数组不正确。
我认为问题在于如何初始化数组的第一个和最后一个。 这里的第一个例子是：
//Store first token in first[][]
if(counter == 1){
first[i][j] = token;
}
这是将名为token的字符串存储到数组的首先[] []的索引[0] [0]中的正确方法吗？
初始化字符串矩阵的正确方法是什么？ 我需要第一行包含名字， 第二行包含第二个名称， 等
我很难想象实际矩阵与它们如何存储在RAM中（我理解数组的名称是指向数组的第一个索引的指针，但当它到达2d数组时，我无法看到指针在RAM中的结构如何
input.txt文件：
Alice Wonderland 1.3 2 3 4 5.5
Bob Marley 7 8 9.8 10 11.5
Charley Manson 12 13.5 14 15 16
代码：
/* Input: input file name, as char array;
matrix of names, and matrix of grades
Functionality: opens the file, extracts names into matrix of names,
extracts grades into the matrix of grades;
Output: 0 if everything went well, -1 otherwise
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAXNUMSTUDENT 100
#define MAXNUMGRADES 100
//#define DEBUG1
#define DEBUG2
char first[MAXNUMSTUDENT][1]; //One first name per row (one column)
char last[MAXNUMSTUDENT][1]; //One last name per row (one column)
float grades[MAXNUMGRADES][MAXNUMGRADES];
float grade;
int counter = 1; //Counts the token number (First two tokens = names, rest = grades)
int i = 0; //Row index
int j = 0; //Column index for first[][], last[][]
int n = 0; //Row index for grades[][]
int m = 0; //Column index for grades[][]
int main(void)
{
//Initialize all arrays to 0
// First[i][j]
for(i=0; i<MAXNUMSTUDENT; i++){
first[i][j] = "0";
for(j=0; j<=1; j++){
first[i][j] = "0";
}
}
// Last[i][j]
for(i=0; i<MAXNUMSTUDENT; i++){
last[i][j] = "0";
for(j=0; j<=1; j++){
last[i][j] = "0";
}
}
// grades[n][m]
for(n=0; n<MAXNUMGRADES; n++){
grades[n][m] = 0;
for(m=0; m<MAXNUMGRADES; m++){
grades[n][m] = 0;
}
}
//Reset indexes
i=0;
j=0;
n=0;
m=0;
FILE * fp;
char * line = NULL;
size_t len = 0;
ssize_t read;
fp = fopen("gradebook.txt", "r"); //Name of input file goes here
if (fp == NULL)
return -1;
//Loops through each line of gradebook (1 loop = 1 line)
while ((read = getline(&line, &len, fp)) != -1) {
/**** AT THIS POINT YOU HAVE A STRING CALLED line *****/
char delim[] = " "; //delimiters are space comma and hyphen
char* token;
//For loop tokenizes string, runs until there are no more tokens
for (token = strtok(line, delim); token; token = strtok(NULL, delim))
{
#ifdef DEBUG1
printf("Retrieved line of length %zu :\n", read);
printf("%s\n", line);
printf("token=%s counter=%d i=%d j=%d n=%d m=%d\n\n", token, counter, i, j, n, m);
#endif
//Store first token in first[][]
if(counter == 1){
first[i][j] = token;
}
//Store second token in last[][]
if(counter == 2){
last[i][j] = token;
//Increment row of first[][] and last[][] (for next line)
i++;
}
//Store the rest of tokens in grades[][]
if(counter > 2){
grade = atof(token);
grades[n][m] = grade;
//Increment column of grades[][]
m++;
}
//Counter for token number
counter++;
}
//Increment row of grades[][]
n++;
//Reset counter
counter = 1;
//Reset column index of grades[][]
m = 0;
}
//Test arrays
printf("Row 1, column 1 of grades: %.2f\n", grades[0][0]);
printf("Row 1, column 1 of first: %c\n", first[0][0]);
printf("Row 1, column 1 of last: %c\n", last[0][0]);
fclose(fp);
if (line)
free(line);
return 0;
}
谢谢。
更新代码：
/* File : extractgrades.c *
* team : SnS *
* Date : 11-20-16 */
/* Input: input file name, as char array;
matrix of names, and matrix of grades
Functionality: opens the file, extracts names into matrix of names,
extracts grades into the matrix of grades;
Output: 0 if everything went well, -1 otherwise
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAXNUMSTUDENT 100
#define MAXNUMGRADES 100
//Comment out to turn off debugging
#define DEBUG1
#define DEBUG2
char first[MAXNUMSTUDENT][MAXNUMSTUDENT];
char last[MAXNUMSTUDENT][MAXNUMSTUDENT];
float grades[MAXNUMGRADES][MAXNUMGRADES];
int numberofscores; //Number of scores
int numberofstudents;
int maxnumberofscores;
int main(void)
{
char first[MAXNUMSTUDENT][MAXNUMSTUDENT] = {{0}};
char last[MAXNUMSTUDENT][MAXNUMSTUDENT] = {{0}};
float grades[MAXNUMGRADES][MAXNUMGRADES] = {{0}};
float grade;
int i; //Row index
int j; //Column index for first[][], last[][]
int n; //Row index for grades[][]
int m; //Column index for grades[][]
int counter; //Counts the token number (First two tokens = names, rest = grades)
//Initialize indexes
counter=1;
numberofscores=0;
i=0;
j=0;
n=0;
m=0;
FILE * fp;
char * line = NULL;
size_t len = 0;
ssize_t read;
fp = fopen("gradebook.txt", "r"); //Name of input file goes here
if (fp == NULL)
return -1;
//Loops through each line of gradebook (1 loop = 1 line)
while ((read = getline(&line, &len, fp)) != -1) {
char delim[] = " "; //delimiters are space comma and hyphen
char * token;
//For loop tokenizes string, runs until there are no more tokens
for (token = strtok(line, delim); token; token = strtok(NULL, delim))
{
#ifdef DEBUG1
printf("Retrieved line of length %zu :\n", read);
printf("%s\n", line);
printf("token=%s counter=%d i=%d j=%d n=%d m=%d\n\n", token, counter, i, j, n, m);
#endif
//Store first token in first[][]
if(counter == 1){
strcpy(first[i], token);
}
//Store second token in last[][]
if(counter == 2){
strcpy(last[i], token);
//Increment row of first[][] and last[][] (for next line)
i++;
}
//Store the rest of tokens in grades[][]
if(counter > 2){
grade = atof(token);
grades[n][m] = grade;
//Increment column of grades[][]
m++;
}
//Counter for token number
counter++;
}
//Save pseudo max number of scores
maxnumberofscores = counter;
if(counter >= maxnumberofscores){
maxnumberofscores = counter;
}
printf("maxnumberofscores: %d\n", maxnumberofscores);
//Increment row of grades[][]
n++;
//Reset column index of grades[][]
m = 0;
//Reset counter
counter = 1;
}
//Get actual max number of scores
numberofscores = maxnumberofscores - 3;
//Get number of students
numberofstudents = i;
//Debug sandwich to test everything
#ifdef DEBUG2
//Test arrays
printf("Row 1, column 1 of grades: %.2f\n", grades[0][0]);
printf("Row 1, column 1 of first: %c\n", first[0][0]);
printf("Row 1, column 1 of last: %c\n", last[0][0]);
//Print all arrays
i=0;
j=0;
n=0;
m=0;
//Print grades[n][m]
for(n=0; n<numberofstudents; n++){
printf("\n");
for(m=0; m<numberofscores; m++){
printf("grades[%d][%d]: %.2f\n", n, m, grades[n][m]);
}
}
//Print first[i][j]
for(i=0; i<numberofstudents; i++){
printf("first[%d]: %s\n", i, first[i]);
}
//Print last[i][j]
for(i=0; i<numberofstudents; i++){
printf("last[%d]: %s\n", i, last[i]);
}
//Print number of scores, number of students
printf("Max number of scores = %d\n", numberofscores);
printf("Number of students: %d\n", numberofstudents);
#endif
fclose(fp);
if (line)
free(line);
return 0;
}
答案 0 :(得分：2)
first[i][j] = "0";
first[i][j]是char（不是字符串），更改为
first[i][j] = '0';
这是将名为token的字符串存储到索引中的正确方法 [0] [0]数组的第一个[] []？
first[i][j] = token;
不，首先，您无法使用=分配数组，您需要使用strcpy之类的功能或更好的更安全的版本，例如strlcpy或{{1} }。
其次，你的数组只有一个字符的空间：
snprintf你需要更多空间：
char first[MAXNUMSTUDENT][1];
另外，您最后会释放char first[MAXNUMSTUDENT][100];
，但每次调用line时都需要调用free以避免内存泄漏：
getline答案 1 :(得分：2)
您的数组声明不正确
char first[MAXNUMSTUDENT][1]
仅分配1个字符的MAXNUMSTUDENT。
对于C，上面只是一个内存块，其大小为MAXNUMSTUDENT个字符，无论您给出的维数是多少。当您取消引用内存块以计算内存块中的偏移量时，将使用这些维度。
您需要的是
char first[MAXNUMSTUDENT][MAX_LENGTH_NAME];
其中MAX_LENGTH_NAME是第一个名称可以包含的字符数加上一个结尾\ 0的字符。其他阵列也是如此。
然而，这看起来像动态内存分配会更好。
因此，不是分配字符数组而是分配一个指向字符串的指针数组。
char* first[MAXNUMSTUDENT]
然后当你strtok行分配并复制字符串
first[i] = strdup(token); // same as malloc/strcpy
我认为如果将所有学生信息放入结构中会更好。
struct student
{
char* first;
char* last;
char* grades;
};
...
struct student students[MAXNUMSTUDENT];
..
students[i].first = strdup(token);
当然你也可以使数组动态化而不是用固定大小声明它，初始大小可以是MAXNUMSTUDENT
struct student** students;
students = malloc(sizeof(struct student*) * MAXNUMSTUDENT);
以后可以使用realloc()