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编程论坛 C图形专区

getchar()在程序中起什么作用

wangdefeng 发布于 2010-11-01 21:10, 1398 次点击
#include <stdio.h>
#define MAXSIZE 10000
#define v 30
typedef struct node
{
    char vert[v];
    int edge[v][v];
    int n,e;
}matrix;
void creatmatrix(matrix *gra)
{
    int p,q,x,w;
    printf("The n and e are:\n");
    scanf("%d%d",&gra->n,&gra->e);
   
    printf("The vertexs are:\n");
    for(p=0;p<gra->n;p++)
        scanf("%c",&gra->vert[p]);
    for(p=0;p<gra->n;p++)
        for(q=0;q<gra->n;q++)
            if(p==q)
                gra->edge[p][q]=0;
            else
                gra->edge[p][q]=MAXSIZE;
            printf("The edges are:\n");
            for(x=0;x<gra->e;x++)
            {
                scanf("%d%d%d",&p,&q,&w);
                gra->edge[p][q]=w;
            }
}
void print(matrix gra)
{
    int p,q;
    printf("\nThe vertexs are:\n");
    for(p=0;p<gra.n;p++)
        printf("%c",gra.vert[p]);
    printf("\n");
    printf("\nThe matrix is:\n");
    for(p=0;p<gra.n;p++)
    {
        for(q=0;q<gra.n;q++)
            printf("%8d",gra.edge[p][q]);
        printf("\n");
    }
}
int main()
{
    matrix gra;
    creatmatrix(&gra);
    print(gra);
    return 0;
}
运行结果:
The n and e are:
3 3
The vertexs are:
ABC
The edges are:

The vertexs are:
AB
The matrix is:
    0  10000  10000
10000      0  10000
10000  10000      0
以上运行结果是错误的。


正确的是:
#include <stdio.h>
#define MAXSIZE 10000
#define v 30
typedef struct node
{
    char vert[v];
    int edge[v][v];
    int n,e;
}matrix;
void creatmatrix(matrix *gra)
{
    int p,q,x,w;
    printf("The n and e are:\n");
    scanf("%d%d",&gra->n,&gra->e);
    getchar();
    printf("The vertexs are:\n");
    for(p=0;p<gra->n;p++)
        scanf("%c",&gra->vert[p]);
    for(p=0;p<gra->n;p++)
        for(q=0;q<gra->n;q++)
            if(p==q)
                gra->edge[p][q]=0;
            else
                gra->edge[p][q]=MAXSIZE;
            printf("The edges are:\n");
            for(x=0;x<gra->e;x++)
            {
                scanf("%d%d%d",&p,&q,&w);
                gra->edge[p][q]=w;
            }
}
void print(matrix gra)
{
    int p,q;
    printf("\nThe vertexs are:\n");
    for(p=0;p<gra.n;p++)
        printf("%c",gra.vert[p]);
    printf("\n");
    printf("\nThe matrix is:\n");
    for(p=0;p<gra.n;p++)
    {
        for(q=0;q<gra.n;q++)
            printf("%8d",gra.edge[p][q]);
        printf("\n");
    }
}
int main()
{
    matrix gra;
    creatmatrix(&gra);
    print(gra);
    return 0;
}
运行结果是:
The n and e are:
3 3
The vertexs are:
ABC
The edges are:
0 2 60
2 0 74
1 2 65
The vertexs are:
ABC
The matrix is:
    0  10000     60
10000      0     65
   74  10000      0
运行正确的程序比运行错误的程序就多了一条"getchar();"语句;
请各位大侠帮我分析一下,十分感谢!



5 回复
#2
zhshxietc2010-11-06 16:00
以前我也遇到过,高手给解答下,感激不尽~
#3
lrr29062872010-11-12 22:40
吃回车?
getchar()把回车吃了?
我也遇到过,两个scanf()的时候好像就要出问题
#4
五当家2010-11-12 23:48
第一个getchar();是接回车的呀!第二个getchar();是用来输出的.
#5
sf_first2010-11-25 17:51
回车在也作为一个字符 被scanf录进去了  所以用getchar()把它接收到;

或者在scanf()后面紧紧跟着一个fflush(stdin);

用这个清除缓冲区也可以
#6
sina_small2012-08-13 19:15
楼上说得也对,不过,fflush( stdin ) 是用在 Visual C++ 6.0 上的

其他的编译器可能不行

楼主发现了这个 Bug ,可以使用2个getchar() 来解决问题,不过逻辑上就不清晰了~~~~~~
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