iphone开发学习，身份证有效性验证

@interface Utility : NSObject
{
}
//验证身份证是否有效
+ (BOOL)checkIDCard:(NSString *)str;
@end

@interface Utility ()
int checkIDfromchar (const char *sPaperId);
@end

@implementation Utility
//验证身份证是否有效
int checkIDfromchar (const char *sPaperId)  
{     
    long lSumQT =0;      
    int R[] ={7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2 };   //加权因子 
    char sChecker[11]={'1','0','X', '9', '8', '7', '6', '5', '4', '3', '2'};  //校验码
    if( 18 != strlen(sPaperId)) return 0;  //检验长度
    //校验数字
    for (int i=0; i<18; i++){
        if ( !isdigit(sPaperId[i]) && !(('X' == sPaperId[i] || 'x' == sPaperId[i]) && 17 == i) ) {
            return 0;
        }
    }
    //验证最末的校验码  
    for (int i=0; i<=16; i++)  {
        lSumQT += (sPaperId[i]-48) * R[i];  
    }
    if (sChecker[lSumQT%11] != sPaperId[17] ){
        return 0;  
    }
    return 1;
} 
+ (BOOL)checkIDCard:(NSString *)str{
    return checkIDfromchar((char *)[str UTF8String]);
}
@end

支持最后一位为X