C中访问数组元素的不同方式 [英] Different way of accessing array elements in C

问题描述

我是 C 编程课程的助教，我遇到了以下 C 代码行:

I am a teaching assistant for a C programming course, and I came across the following line of C code:

char str[] = "My cat's name is Wiggles.";
printf("%c %c %c %c\n", str[5], *(str + 5), *(5 + str), 5[str]);

我之前从未遇到过最后一个参数 (5[str])，我的教授也没有遇到过.我认为 K&R 和 C Primer Plus 中没有提到它.我在一组技术面试问题中找到了这段代码.有谁知道为什么 C 也允许您以这种方式访问​​数组元素?我从来没有听说过括号外的索引和括号内的数组名.

I never came across the very last argument (5[str]) before, and neither did my professor. I don't think it's mentioned in K&R and C Primer Plus. I found this piece of code in a set of technical interview questions. Does anyone know why C allows you to access an array element that way also? I never heard of an index being outside the set of brackets and the name of an array inside the brackets.

非常感谢您的帮助！

推荐答案

完全有效的 C.来自 维基百科:

Perfectly valid C. From Wikipedia:

同样，由于表达式 a[i] 在语义上等价于 *(a+i)，而后者又等价于 *(i+a)，因此该表达式也可以写成 i[a](虽然这表格很少使用).

Similarly, since the expression a[i] is semantically equivalent to *(a+i), which in turn is equivalent to *(i+a), the expression can also be written as i[a] (although this form is rarely used).

古怪，但有效.

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