92 lines
2.8 KiB
Java
92 lines
2.8 KiB
Java
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import java.util.*;
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public class Node {
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private String name;
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private Node firstChild;
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private Node nextSibling;
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Node (String n, Node d, Node r) {
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this.name = n;
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this.firstChild = d;
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this.nextSibling = r;
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}
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public static Node parsePostfix (String s) {
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if (s.contains(",,")) {
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throw new RuntimeException("double commas");
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} else if (s.contains("\t")) {
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throw new RuntimeException("tab char");
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} else if (s.contains("()")) {
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throw new RuntimeException("empty subtree");
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} else if (s.contains(" ")) {
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throw new RuntimeException("space");
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} else if (s.contains("((") && s.contains("))")) {
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throw new RuntimeException("Brackets");
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} else if (s.contains(",") && !(s.contains("(") && s.contains(")"))) {
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throw new RuntimeException("two roots");
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}
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String[] tokens = s.split("");
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Stack<Node> stack = new Stack();
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Node node = new Node(null, null, null);
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boolean replacingRoot = false;
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for (int i = 0; i < tokens.length; i++) {
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String token = tokens[i].trim();
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if (token.equals("(")) {
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if (replacingRoot) {
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throw new RuntimeException("Trying to replace root");
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}
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stack.push(node);
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node.firstChild = new Node(null, null, null);
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node = node.firstChild;
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if (tokens[i+1].trim().equals(",")) {
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throw new RuntimeException("comma after node");
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}
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} else if (token.equals(")")) {
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node = stack.pop();
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if (stack.size() == 0) {
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replacingRoot = true;
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}
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} else if (token.equals(",")) {
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if (replacingRoot) {
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throw new RuntimeException("Trying to replace root");
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}
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node.nextSibling = new Node(null, null, null);
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node = node.nextSibling;
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} else {
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if (node.name == null) {
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node.name = token;
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} else {
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node.name += token;
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}
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}
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}
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return node;
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}
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public String leftParentheticRepresentation() {
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StringBuilder sb = new StringBuilder();
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sb.append(this.name);
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if (this.firstChild != null) {
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sb.append("(");
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sb.append(this.firstChild.leftParentheticRepresentation());
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sb.append(")");
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}
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if (this.nextSibling != null) {
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sb.append(",");
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sb.append(this.nextSibling.leftParentheticRepresentation());
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}
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return sb.toString();
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}
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public static void main (String[] param) {
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String s = "(B1,C)A";
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Node t = Node.parsePostfix (s);
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String v = t.leftParentheticRepresentation();
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System.out.println (s + " ==> " + v); // (B1,C)A ==> A(B1,C)
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}
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}
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