putchar()可以打印整数吗? [英] Can putchar() print an integer?

问题描述

如何仅在putchar()的帮助下打印整数.我想在不使用外部存储的情况下做到这一点.
去年的一次采访中问了这个问题.

How can I print an integer with the help of putchar() only. i want to do it without using external storage.
This question was asked in an interview last year.

推荐答案

在面试中遇到含糊的要求时，表达您的假设是个好主意.

When faced with vague requirements on an interview, it's a good idea to express your assumptions.

我只能使用putchar来表示它是唯一允许我调用的库函数.我还要进一步假设没有外部存储"意味着我无法显式创建缓冲区.如果访问者同意我的假设，我将继续:

I would take the requirement about only being able to use putchar to mean that it is the only library function I am allowed to call. I would furthermore assume that "no external storage" meant that I could not explicitly create a buffer. If the interviewer agreed with my assumptions, I would proceed with:

void pr_int(int n) {
    if (n < 0) {
        putchar('-');
        n = -n;
    }
    if (n / 10 != 0)
        pr_int(n / 10);
    putchar((n % 10) + '0');
}

如果面试官随后评论说n = -n;对于INT_MIN失败，如下所述，那么我将其重写为:

If the interviewer then commented that n = -n; would fail for INT_MIN, as noted below, then I would rewrite it as:

void pr_uint(unsigned int n) {
    if (n / 10 != 0)
        pr_uint(n / 10);
    putchar((n % 10) + '0');
}

void pr_int(int n) {
    if (n < 0) {
        putchar('-');
        n = -n;
    }
    pr_uint((unsigned int) n);
}

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