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Copy pathLetterCombinations.java
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54 lines (50 loc) · 1.68 KB
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package leetcode.string;
import java.util.ArrayList;
import java.util.List;
/*
* @description: 17.电话号码的字母组合
* @param: 数字字符串
* @return: 九空格所有字符组合
* @author: cp
* @date: 2020/8/30
*/
public class LetterCombinations {
public List<String> letterCombinations(String digits) {
List<String> result = new ArrayList<>();
if (digits.isEmpty()) {
return result;
}
String[] letter = {"", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
List<String>[] digitList = getListArray(letter);
for (int i = 0; i < digits.length(); i++) {
List<String> charList = digitList[digits.charAt(i) - '0'];
result = multiply(result, charList);
}
return result;
}
//字符串转链表
private List<String>[] getListArray(String[] letters) {
List<String>[] letterList = new ArrayList[letters.length];
for (int i = 0; i < letters.length; i++) {
String digit = letters[i];
List<String> result = new ArrayList<>();
for (int j = 0; j < digit.length(); j++) {
result.add(digit.charAt(j) + "");
}
letterList[i] = result;
}
return letterList;
}
//链表相乘
private List<String> multiply(List<String> l1, List<String> l2) {
if (l1.isEmpty() || l2.isEmpty()) {
return l1.isEmpty() ? l2 : l1;
}
List<String> ans = new ArrayList<>();
for (int i = 0; i < l1.size(); i++)
for (int j = 0; j < l2.size(); j++) {
ans.add(l1.get(i) + l2.get(j));
}
return ans;
}
}