[2011山东ACM省赛] Identifiers（模拟）

Identifiers

Time Limit: 1000ms   Memory limit: 65536K  有疑问？点这里^_^

题目描述

 Identifier is an important concept in the C programming language. Identifiers provide names for several language elements, such as functions, variables, labels, etc.

An identifier is a sequence of characters. A valid identifier can contain only upper and lower case alphabetic characters, underscore and digits, and must begin with an alphabetic character or an underscore. Given a list of chararcter sequences, write a program to check if they are valid identifiers.

输入

 The first line of the input contains one integer, N, indicating the number of strings in the input. N lines follow, each of which contains at least one and no more than 100 characters. (only upper and lower case alphabetic characters, digits, underscore (" "), hyphen ("-"), period ("."), comma (","), colon (":"), semicolon (";"), exclamation mark ("!"), question mark ("?"), single and double quotation marks, parentheses, white space and square brackets may appear in the character sequences.)

输出

For each of the N lines, output "Yes" (without quote marks) if the character sequence contained in that line make a valid identifier; output "No" (without quote marks) otherwise.

示例输入

7
ValidIdentifier
valid_identifier
valid_identifier
0 invalid identifier
1234567
invalid identifier
adefhklmruvwxyz12356790 -.,:;!?'"()[]ABCDGIJLMQRSTVWXYZ

示例输出

Yes
Yes
Yes
No
No
No
No

提示

 

来源

山东省第二届ACM大学生程序设计竞赛

 

解题思路：

判断是否输入的字符串为合法标识符。

代码：

#include 
#include 
#include 
#include 
using namespace std;
string str[1000];
int main()
{
    int n;cin>>n;
    getchar();//必须得加这个,吸收空格，否则后面用getline会出错
    for(int i=1;i<=n;i++)
    {
        getline(cin,str[i]);
        bool ok=1;
        int len=str[i].length();
        if(!isalpha(str[i][0])&&str[i][0]!='_')//首字母不是字母也不是下划线
        {
            cout<<"No"<