获取值在目标C中的最高有效位 [英] Getting a values most significant digit in Objective C

问题描述

我目前在目标C中有代码，可以提取整数的最高有效数字值.我唯一的问题是，是否有比我下面提供的方法更好的方法.它可以完成工作，但是感觉就像是廉价的黑客一样.

I currently have code in objective C that can pull out an integer's most significant digit value. My only question is if there is a better way to do it than with how I have provided below. It gets the job done, but it just feels like a cheap hack.

该代码的作用是接受一个传入的数字并循环通过，直到将该数字成功划分为某个值为止.我这样做的原因是针对一个教育性应用程序，该应用程序将其值除以一个数字，并显示所有加在一起的值以产生最终输出(1234 = 1000 + 200 + 30 + 4).

What the code does is that it takes a number passed in and loops through until that number has been successfully divided to a certain value. The reason I am doing this is for an educational app that splits a number up by it's value and shows the values added all together to produce the final output (1234 = 1000 + 200 + 30 + 4).

int test = 1;
int result = 0;
int value = 0;

do {
    value = input / test;
    result = test;
    test = [[NSString stringWithFormat:@"%d0",test] intValue];
} while (value >= 10);

任何建议总是倍受赞赏.

Any advice is always greatly appreciated.

推荐答案

这可以解决这个问题吗?

Will this do the trick?

int sigDigit(int input)
{
    int digits =  (int) log10(input);
    return input / pow(10, digits);
}

基本上，它会执行以下操作:

Basically it does the following:

1. 找出输入(log10(input))中的位数并将其存储在位数"中.
2. 将input除以10 ^ digits.

1. Finds out the number of digits in input (log10(input)) and storing it in 'digits'.
2. divides input by 10 ^ digits.

您现在应该拥有数字中最重要的数字.

You should now have the most significant number in digits.

如果您需要一个在特定索引处获取整数值的函数，请将该函数签出:

in case you need a function that get the integer value at a specific index, check this function out:

int digitAtIndex(int input, int index)
{
    int trimmedLower = input / (pow(10, index)); // trim the lower half of the input

    int trimmedUpper = trimmedLower % 10; // trim the upper half of the input
    return trimmedUpper;
}

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