Question

我正在尝试从文件中读取图形，我在节点的第一行找到了，我创建了一个代码，用于读取向量中的节点，直到行结束，然后在第二行，就像我得到了弧形，（％d％d）格式。我的问题是，当我尝试读取节点时，它会跳过第一个数字，第三个，依此类推。我无法弄清楚原因。这是我的代码：

void readGraph() {
    int i=0, j, node1, node2, n,check1, check2,c;
    char nodes[MAXN];
    FILE *f;

    f = fopen("data.in","r");

    if (f == NULL) {
        printf("Error in opening file!");
    }
    else {

       while ((c = fgetc(f)) != EOF) {

            if ( c != ' ') {
                fscanf(f, "%d", &(nodes[i]));
                printf("%d, %d\n",i,nodes[i]);
                i++;
            }

            if (c == '\n')
                break;

        }
    }

    while (fscanf(f,"(%d %d)", &node1, &node2)) {

        if ( c != ' ')
            fscanf(f, "(%d %d) ", &node1, &node2);

        if (c == '\n')
            break;

   }
   fclose(f);
}

另外，我的data.in：

1 2 3 4 5 6
(1 3) (2 3) (3 4) (3 5) (3 6) (4 6) (5 6)

任何帮助将不胜感激。谢谢！

Answer 1

我猜，fgetc逐字节读取，而fscanf（＆＃34;％d＆＃34;）一次读取4个字节，所以这可能会导致一些问题。

Answer 2

   while ((c = fgetc(f)) != EOF) {

        if ( c != ' ') {
            fscanf(f, "%d", &(nodes[i]));
            printf("%d, %d\n",i,nodes[i]);
            i++;
        }

        if (c == '\n')
            break;

    }

这里你从f读了两次（fgetc(f)被丢弃）

对于弧线（下面的代码），这也是一个问题，你测试c但是你不再读它了

    while (fscanf(f,"(%d %d)", &node1, &node2)) {

        if ( c != ' ')
            fscanf(f, "(%d %d) ", &node1, &node2);

        if (c == '\n')
            break;

   }

Answer 3

void readGraph(void){
    int i = 0, j, node1, node2, n, check1, check2, c;
    int nodes[MAXN];
    FILE *f;

    f = fopen("data.in","r");

    if (f == NULL) {
        printf("Error in opening file!");
        return ;
    }

    while ((c = fgetc(f)) != EOF) {
        if( c == ' ')
            continue;
        else if( c == '\n')
            break;
        else {
            ungetc(c, f);//It is too reading. So Return the character to the stream.
            fscanf(f, "%d", &nodes[i]);
            printf("%d, %d\n", i, nodes[i]);
            i++;
        }
    }

    while (2 == fscanf(f,"(%d %d) ", &node1, &node2)) {
        printf("(%d, %d)\n", node1, node2);
    }
    fclose(f);
}

Answer 4

尝试此解决方案，您可以看到我的c评论：

void readGraph() {
    int i=0, j, node1, node2, n,check1, check2,c;
    char nodes[128];
    FILE *f;

    f = fopen("data.in","r");

    if (f == NULL) {
        printf("Error in opening file!");
    }
    else {

       while (((c = fgetc(f)) != EOF) && (c != '\n')) {

            if ( c != ' ') {
                nodes[i] = c;
                /*fscanf(f, "%d", &(nodes[i]));*/ // you loose read c value when you read again without using value
                printf("%d, %c\n",i,nodes[i]);
                i++;
            }

            /*if (c == '\n')
                break;*/ 
            /* You loop 1 extra time */

        }
    }

    while (fscanf(f,"(%d %d)", &node1, &node2)) {

        if ( c != ' ')
            fscanf(f, "(%d %d) ", &node1, &node2);

        if (c == '\n')
            break;

   }
   fclose(f);
}

从文件问题中读取

4 个答案: