c语言a b简单程序,C语言数组a[b]=b[a]。。。。

int a[5] = {1,2,3,4,5};

int b = 3;

发现 a[b]=*(a+b)=*(b+a)=b[a];   利用指针运算交换律，感觉C的指针很灵活，在java中就不行。

官方讲解：

A postfix expression followed by an expression in [ ] (brackets) specifies an element of an array. The expression within the brackets is referred to as asubscript. The first element of an array has the subscript zero.

By definition, the expression a[b] is equivalent to the expression *((a) + (b)), and, because addition is associative, it is also equivalent to b[a]. Between expressions a and b, one must be a pointer to a type T, and the other must have integral or enumeration type. The result of an array subscript is an lvalue. The following example demonstrates this:

#include

int main(void) {

int a[3] = { 10, 20, 30 };

printf("a[0] = %d\n", a[0]);

printf("a[1] = %d\n", 1[a]);

printf("a[2] = %d\n", *(2 + a));

return 0;

}

The following is the output of the above example:

a[0] = 10

a[1] = 20

a[2] = 30