如题

这个简单，就不给你原题了，给你个思路，用字符串数组，判断数组的第一个元素是否为字母或者下划线，然后逐个判断是否为字母、数字、下划线，遇到\0后结束，我劝你还是自己多动动脑子，不要一味的索取答案

是不是忘了还不能是关键字！

嗯，32个关键字必须一个一个的输入进去，用字符串数组对比，楼上的谢谢提醒了

唉     是一点都不会

你稍等一下，我试着做一下

这道题做起来有点麻烦，呵呵

#include<stdio.h>
#include<string.h>
main()
{
    char a[32][10]={"auto","break","case","char","const","continue","default","do","double","else","enum","extern","float","for","goto","if","int","long","register","return","short","signed","sizeof","static","struct","switch","typedef","union","unsigned","void","volatile","while"};
    int i,x=1;
    char in[30];/*长度30应该够了*/
    printf("请输入一串字符串判断是否为合法标识符:\n");
    gets(in);
    if(in[0]=='_'||(in[0]>='a'&&in[0]<='z')||(in[0]>='A'&&in[10]<='Z')){//3
        for(i=0;i<32;i++){//2
            if((strcmp(a[i],in))==0){//1
                x=0;
                break;
            }//1
        }//2
    }//3
    if(x==0)
        printf("no");
    else
        printf("yes");
}

yes是正确的标识符，no不是

#include<stdio.h>
#include<string.h>
main()
{
    char a[32][10]={"auto","break","case","char","const","continue","default","do","double","else","enum","extern","float","for","goto","if","int","long","register","return","short","signed","sizeof","static","struct","switch","typedef","union","unsigned","void","volatile","while"};
    int i,x=1;
    char in[30];/*长度30应该够了*/
    printf("请输入一串字符串判断是否为合法标识符:\n");
    gets(in);
    if(in[0]=='_'||(in[0]>='a'&&in[0]<='z')||(in[0]>='A'&&in[10]<='Z')){//3
        for(i=0;i<32;i++){//2
            if((strcmp(a[i],in))==0){//1
                x=0;
                break;
            }//1
        }//2
    }//3
    if(x==0)
        printf("it is a illeg.\n");
    else
        printf("it is a legal identifier.\n");
}