Letter combinations of a phone number
Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent. Return the answer in any order.
A mapping of digits to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.
/**
* @param {string} digits
* @return {string[]}
*/
var letterCombinations = function(digits) {
if (!digits.length) {
return [];
}
const digitToLetters = {
'2': 'abc',
'3': 'def',
'4': 'ghi',
'5': 'jkl',
'6': 'mno',
'7': 'pqrs',
'8': 'tuv',
'9': 'wxyz'
};
const res = [];
function backtrack(idx, comb) {
if (idx === digits.length) {
res.push(comb);
return;
}
for (const letter of digitToLetters[digits[idx]]) {
backtrack(idx + 1, comb + letter);
}
}
backtrack(0, "");
return res;
//in video above, BFS is used instead of dfs/backtracking
const map = digitToLetters;
cont queue = ['']
for (const digit of digits) {
const len = queue.length;
for (let i = 0; i<len; i++) {
const current = queue.shift();
map[digit].split('').forEach(i => queue.push(current+i))
}
}
return queue;
};Related Problems
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The same number may be chosen from candidates an unlimited number of times. Two combinations are unique if the frequency of at least one of the chosen numbers is different.
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You are given a list of strings words from the alien language's dictionary, where the strings in words are sorted lexicographically by the rules of this new language.
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