java - 检查给定字符串是否与其他两个字符串交错

Question

我编写了检查 S3 是否是 S1 和 S2 字符串的交错代码。

但是对于像 "AB", "CD"-> "ACBD"这样的简单字符串它会失败

我错过了什么吗？

class InterleavedString {

    // error
    public static boolean isInterleaved (String A, String B, String C)
    {
        // Iterate through all characters of C.
        int a = 0, b = 0, c = 0;
        while (C != null)
        {
            // Match first character of C with first character of A,
            // If matches them move A to next 
            if (A.charAt(a) == C.charAt(c))
                a++;

            // Else Match first character of C with first character of B,
            // If matches them move B to next 
            else if (B.charAt(b) == C.charAt(c))
                b++;

            // If doesn't match with either A or B, then return false
            else
                return false;

            // Move C to next for next iteration
            c++;
        }

        // If A or B still have some characters, then length of C is smaller 
        // than sum of lengths of A and B, so return false
        if (A != null || B != null)
            return false;

        return true;
    }

    public static void main(String [] args) {
        String A = "AB", B = "CD", C = "ACBD";
        System.out.println(isInterleaved(A, B, C));
    }
}

错误:

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 2 at java.lang.String.charAt(Unknown Source) at strings.InterleavedString.isInterleaved(InterleavedString.java:14) at strings.InterleavedString.main(InterleavedString.java:40)

已编辑:

while (c != C.length())
.....
.....
if (a != A.length() || b != B.length())

Answer 1

您的while 语句的条件是错误的。您永远不会更改 C 的值。而不是 while (C != null) 你应该使用 while c != C.length() 或类似的东西。

您的 A != null 和 B != null 语句也存在同样的问题，因为 charAt 不会删除任何字符!

此外，您需要在 if 子句中检查 Strings 的边界:

if (a < A.length() && A.charAt(a) == C.charAt(c))

此外，如果您的目标是提高效率，您应该在方法的开头添加此检查，然后删除最后的 if 语句:

if (A.length() + B.length() != C.length())
    return false;