什么是真正的用途使用N [C-'0']的？ [英] What's the real use of using n[c-'0']?

问题描述

我在C新手，我整个code来是这样的：

I'm a novice in C and I came across the code like this :

int n[10];
if(c>='0' && c<='9')
++n[c-'0']

在如果循环为什么我们要使用左右 0 单引号，有什么用呢，我们为什么不能定义 0 为一个整数直线距离？而在code的第二行 ++ N [C-'0'] ，有什么用使用数组像这样，在某种意义上我们为什么需要减去 0 （再次为什么在这种情况下使用单引号的？）在数组索引从 C ？

In if loop why we have to use single quotes around 0, whats the use of it, why we can't define 0 as an integer straight away? And in the second line of code ++n[c-'0'], whats the use of using array like this, in sense why we need to subtract 0(once again why the use of single quotes in this context?) from c in the array index?

如果我做这样的 N [C-'0'] ，索引操作（结果 C-'0）将是一个字符或整数？

If i do like this n[c-'0'], the result of index operation(c-'0') will be an character or integer?

由于任何人都可以说我，什么真正使用这种阵列和哪些缺点呢？

Given that can anyone say me, whats the real use of such array and what are the disadvantages well?

先谢谢了。

推荐答案

在C， 0 是一个整数，其价值重估presents数字为零一个字符，而不是0值，这将是空字符。其他答案省略了这一点，但要注意，重要的是C语言任务的十进制数字已经连续值，因此，如果 C 是一个数字， C-'0 是位的数值，即

In C, '0' is an integer whose value represents the digit zero as a character, not the value 0, which would be the null character. Other answers have omitted this, but it's important to note that the C language mandates that the decimal digits have consecutive values, so that if c is a digit, c-'0' is the numeric value of that digit, i.e.

'0'-'0' = 0
'1'-'0' = 1
'2'-'0' = 2
.
.
.
'9'-'0' = 9

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