C# 了解如何向后遍历字符串

Question

我正在学习 c# 类(class)，它为我提供了一些我可以复制和粘贴的代码，还有一些是我自己编写的。无论如何，我不明白在这个 for() 循环中为什么我们要从 int i = target.Length 属性中减去 1？

static string reverseString(string target)
{
    String result = "";

    // walk the target string backwards
    for (int i = target.Length - 1; i >= 0; i--)
    {
        // add this letter to the result
        result += target[i];
    }

    // return the result to the calling code
    return result;
}

Answer 1

举个例子。

string target = "ABC";
// target can be thought of as an array of characters
// target[0] holds 'A'
// target[1] holds 'B'
// target[2] holds 'C'

int length = target.Length; 
// length would be 3 because Length is the count of the chars
// but if you were to try and get the value of target[3] you would get an error 
// because target ends at [2] (index 2)

因此您需要从 .Length - 1 开始并向后计算到 0(而不是 1)。