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17. 电话号码的字母组合 #9

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Description

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17. 电话号码的字母组合

Description

Difficulty: 中等

Related Topics: 哈希表, 字符串, 回溯

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。

Solution

Language: JavaScript

/**
 * @param {string} digits
 * @return {string[]}
 */

var letterCombinations = function (digits) {
    if (digits.length === 0) return []
    const res = []
    const map = ['', '', 'abc', 'def', 'ghi', 'jkl', 'mno', 'pqrs', 'tuv', 'wxyz']
    const dfs = (curStr, i) => {
        if (i > digits.length - 1) {
            res.push(curStr)
            return
        }
        const letters = map[digits[i]]
        for (const l of letters) {
            dfs(curStr + l, i + 1)
        }
    }
    dfs('', 0)
    return res
}

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