Letter Combinations of Phone Number problem & test cases, Word Search problem

Backtracking/LetterCombos.js

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+function letterCombinations(digits) {
+ if (digits === '') {
+ // base case
+ return []
+ }
+
+ const dic = {
+ 2: 'abc',
+ 3: 'def',
+ 4: 'ghi',
+ 5: 'jkl',
+ 6: 'mno',
+ 7: 'pqrs',
+ 8: 'tuv',
+ 9: 'wxyz'
+ }
+
+ const res = [] // letter combinations to return
+ const combo = []
+
+ function backtrack(i) {
+ if (i === digits.length) {
+ res.push(combo.join(''))
+ return
+ }
+
+ for (const c of dic[digits[i]]) {
+ combo.push(c)
+ backtrack(i + 1)
+ combo.pop()
+ }
+ }
+
+ backtrack(0)
+ return res
+}
+
+export { letterCombinations }

Backtracking/WordSearch.js

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+function exist(board, word) {
+ const ROWS = board.length;
+ const COLS = board[0].length;
+ const visited = new Set();
+
+ function backtrack(row, col, idx) {
+ if (idx === word.length) {
+ return true;
+ }
+
+ if (!(0 <= row && row < ROWS && 0 <= col && col < COLS && !visited.has(`${row},${col}`)
+ && idx < word.length && board[row][col] === word[idx])) {
+ return false;
+ }
+
+ visited.add(`${row},${col}`);
+ const res = (backtrack(row - 1, col, idx + 1) || backtrack(row + 1, col, idx + 1) ||
+ backtrack(row, col - 1, idx + 1) || backtrack(row, col + 1, idx + 1));
+ visited.delete(`${row},${col}`);
+ return res;
+ }
+
+ for (let row = 0; row < ROWS; row++) {
+ for (let col = 0; col < COLS; col++) {
+ if (board[row][col] === word[0] && backtrack(row, col, 0)) {
+ return true;
+ }
+ }
+ }
+
+ return false;
+}
+
+export {exist}

Backtracking/tests/LetterCombos.test.js

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+import { letterCombinations } from '../LetterCombos'
+
+describe('LetterCombinations', () => {
+ it('Letter Combinations of 23', () => {
+ const res = letterCombinations('23')
+ expect(res).toEqual(['ad', 'ae', 'af', 'bd', 'be', 'bf', 'cd', 'ce', 'cf'])
+ })
+
+ it('Letter Combinations of empty string', () => {
+ const res = letterCombinations('')
+ expect(res).toEqual([])
+ })
+
+ it('Letter Combinations of 2', () => {
+ const res = letterCombinations('2')
+ expect(res).toEqual(['a', 'b', 'c'])
+ })
+})