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Commit f8d1281

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solved: Letter combinations of a phone number
1 parent fb2902f commit f8d1281

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‎README.md‎

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- [Text Justification](#text-justification)
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- [3 Sum](#3-sum)
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- [3 Sum Closest](#3-sum-closest)
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- [Letter combinations of a phone number](#letter-combinations-of-a-phone-number)
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### String to Int - Atoi
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@@ -676,4 +677,46 @@ int threeSumClosest(List<int> nums, int target) {
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return result;
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}
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```
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### Letter combinations of a phone number
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```dart
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const Map<int, List<String>> chars = {
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2: ['a', 'b', 'c'],
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3: ['d', 'e', 'f'],
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4: ['g', 'h', 'i'],
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5: ['k', 'j', 'l'],
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6: ['m', 'n', 'o'],
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7: ['p', 'q', 'r', 's'],
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8: ['t', 'u', 'v'],
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9: ['w', 'x', 'y', 'z'],
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};
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List<String> letterCombinations(String digits) {
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if (digits.isEmpty) return [];
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final List<String> result = [];
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lookupChar(0, "", digits.length, digits, result);
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return result;
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}
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void lookupChar(
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int index,
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String res,
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int length,
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String digits,
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List<String> result,
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) {
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if (index == digits.length)
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result.add(res);
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else {
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final List<String> letters = chars[int.parse(digits[index])]!;
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for (int i = 0; i < letters.length; i++) {
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lookupChar(index + 1, res + letters[i], length, digits, result);
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}
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}
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}
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```
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void main(List<String> args) {
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List<String> cases = ["23", "", "2", "9"];
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for (final testcase in cases) {
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print(letterCombinations(testcase));
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}
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}
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const Map<int, List<String>> chars = {
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2: ['a', 'b', 'c'],
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3: ['d', 'e', 'f'],
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4: ['g', 'h', 'i'],
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5: ['k', 'j', 'l'],
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6: ['m', 'n', 'o'],
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7: ['p', 'q', 'r', 's'],
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8: ['t', 'u', 'v'],
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9: ['w', 'x', 'y', 'z'],
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};
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List<String> letterCombinations(String digits) {
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if (digits.isEmpty) return [];
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final List<String> result = [];
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lookupChar(0, "", digits.length, digits, result);
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return result;
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}
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void lookupChar(
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int index,
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String res,
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int length,
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String digits,
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List<String> result,
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) {
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if (index == digits.length)
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result.add(res);
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else {
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final List<String> letters = chars[int.parse(digits[index])]!;
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for (int i = 0; i < letters.length; i++) {
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lookupChar(index + 1, res + letters[i], length, digits, result);
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}
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}
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}

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