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17. 电话号码的字母组合
给定一个仅包含数字 2-9 的字符串,返回所有它能表示的字母组合。答案可以按 任意顺序 返回。
给出数字到字母的映射如下(与电话按键相同)。注意 1 不对应任何字母。
示例 1:
输入:digits = "23"
输出:["ad","ae","af","bd","be","bf","cd","ce","cf"]
示例 2:
输入:digits = ""
输出:[]
示例 3:
输入:digits = "2"
输出:["a","b","c"]
提示:
0 <= digits.length <= 4
digits[i] 是范围 ['2', '9'] 的一个数字。
- 来源:力扣(LeetCode)
- 链接:https://leetcode.cn/problems/letter-combinations-of-a-phone-number
javascript
/**
* @param {string} digits
* @return {string[]}
*/
var letterCombinations = function(digits) {
if(digits.length === 0) return []
const digitsMap = {
2: ['a','b','c'],
3: ['d','e','f'],
4: ['g','h','i'],
5: ['j','k','l'],
6: ['m','n','o'],
7: ['p','q','r','s'],
8: ['t','u','v'],
9: ['w','x','y','z']
}
if(digits.length === 1) return digitsMap[digits[0]]
let i = 1, res = digitsMap[digits[0]].slice()
while(i < digits.length) {
const letters = digitsMap[digits[i]], len = res.length
for (let k = 0; k < len; k++) {
const str = res.shift()
for (let j = 0; j < letters.length; j++) {
res.push(str + letters[j])
}
}
i++
}
return res
}
console.log(letterCombinations('22'))
console.log(letterCombinations('234'))
console.log(letterCombinations('23'))
console.log(letterCombinations('2'))
console.log(letterCombinations(''))