Answer 1

Answer 2

Answer 3

[此代码显然不需要解释]

(void)convertBinaryToNumeric{
    NSString *bin_Input = @"1010";
    NSString *reverseInput = [self reverseString:bin_Input];
    int dec_Output = 0;
    int dec_Counter = 0;

    for (int i=0; i<[reverseInput length]; i++) {
        dec_Output = [[reverseInput substringWithRange:NSMakeRange(i, 1)] intValue] * [self multipliesByTwo:i];
        dec_Output = dec_Counter + dec_Output;
        dec_Counter = dec_Output;
    }
    NSLog(@"Bin:%@ Dec:%d",bin_Input,dec_Output);
}

(NSString *)reverseString:(NSString *)inputStr{
    NSMutableString *revStr = [[NSMutableString alloc]initWithString:@""];
    for (int i=[inputStr length]-1; i>=0; i--) {
        [revStr appendString:[inputStr substringWithRange:NSMakeRange(i, 1)]];
    }
    return revStr;
}

(int)multipliesByTwo:(int)number{
    if(number == 0){
        return 1;
    }else{
        int bin_value = 2;
        int multipleBy=0;
        for (int i=1; i<=number; i++) {
            if(multipleBy == 0){
                multipleBy = bin_value;
            }else{
                multipleBy = multipleBy *2;
            }
        }
        return multipleBy;
    }
    return 0;
}