67 lines
1.4 KiB
Java
67 lines
1.4 KiB
Java
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package com.cool.hot100.backtracking;
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import java.util.*;
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/**
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* Created with IntelliJ IDEA.
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*
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* @Author: Cool
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* @Date: 2024/09/10/11:06
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* DayNumber 1
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* Hard 2
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* Level ?
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*/
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public class Num17 {
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List<String> res = new ArrayList<>();
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char[] chars;
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public List<String> letterCombinations(String digits) {
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if ("".equals(digits)) {
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return new ArrayList<>();
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}
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chars = new char[digits.length()];
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dfs(0, digits);
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return new ArrayList<>(res);
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}
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private void dfs(int index, String digits) {
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if (index >= digits.length()) {
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res.add(new String(chars));
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return;
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}
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String str = getLetter(digits.charAt(index)-'0');
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for (int i = 0; i < str.length(); i++) {
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chars[index] = str.charAt(i);
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dfs(index + 1, digits);
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}
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}
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private String getLetter(int num) {
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switch (num) {
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case 2:
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return "abc";
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case 3:
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return "def";
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case 4:
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return "ghi";
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case 5:
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return "jkl";
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case 6:
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return "mno";
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case 7:
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return "pqrs";
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case 8:
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return "tuv";
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case 9:
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return "wxyz";
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default:
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return "";
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}
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}
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}
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