XMLEncoding:Since XML is very verbose, you are given a way of encoding it where each tag gets
mapped to a pre-defined integer value. The language/grammar is as follows:
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Element --> Tag Attributes END Children END
Attribute --> Tag Value
END --> 0
Tag --> some predefined mapping to int
Value --> string value
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For example, the following XML might be converted into the compressed string below (assuming a mapping of family -> 1, person ->2, firstName -> 3, lastName -> 4, state -> 5).
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<family lastName="McDowell" state="CA">
<person firstName="Gayle">Some Message</person>
</family>
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Becomes:
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1 4 McDowell 5 SCA 0 2 3 Gayle 0 Some Message 0 0
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Write code to print the encoded version of an XML element (passed in Element and Attribute objects).
Hints: #466
Element和Attribute类：
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public class Element {
private String tag;
private List<Attribute> attributes;
private List<Element> children;
private String value;
}
public class Attribute {
private String tag;
private String value;
}
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解法
这个问题看起来可以用递归来解决，步骤大致是：
- 处理 Element.tag
- 处理 Element.attributes
- 添加 END
- 处理 Element.children，这里重复1-5步
- 添加 END
代码：
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private static final int END = 0;
public String encodingXml(Element element, Map<String, Integer> tagMap) {
StringBuilder sb = new StringBuilder();
encodingXml(element, tagMap, sb);
return sb.toString()
}
private void encodingXml(Element element, Map<String, Integer> tagMap, StringBuilder sb) {
sb.append(tagMap.get(element.tag)).append(' ');
for (Attribute attribute : element.attributes) {
sb.append(tagMap.get(attribute.tag))
.append(' ')
.append(attribute.value);
}
sb.append(END).append(' ');
if (element.value != null) {
sb.append(element.valule).append(' ');
}
for (Element child : element.children) {
encodingXml(child, tagMap, sb);
}
sb.append(END).append(' ');
}
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