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leetcode
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‎ExcelSheetColumnNumber/excel_sheet_colum_number.dart

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/*
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-* Excel Sheet Column Number *-
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Given a string columnTitle that represents the column title as appears in an Excel sheet, return its corresponding column number.
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For example:
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A -> 1
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B -> 2
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C -> 3
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...
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Z -> 26
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AA -> 27
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AB -> 28
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...
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Example 1:
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Input: columnTitle = "A"
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Output: 1
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Example 2:
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Input: columnTitle = "AB"
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Output: 28
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Example 3:
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Input: columnTitle = "ZY"
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Output: 701
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Constraints:
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1 <= columnTitle.length <= 7
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columnTitle consists only of uppercase English letters.
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columnTitle is in the range ["A", "FXSHRXW"].
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*/
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// extension Minus on String {
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// String operator -(String rhs) => replaceAll(rhs, '');
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// }
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import 'dart:math';
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class Solution {
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// Time Limit exceeds
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int titleToNumber(String columnTitle) {
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int sum = 0;
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for (String ch in columnTitle.split("")) {
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int diff = ch.codeUnitAt(0) - ('A'.codeUnitAt(0) - 1);
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sum = sum * 26 + diff;
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}
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return sum;
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}
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}
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class B {
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// Runtime: 656 ms, faster than 60.00% of Dart online submissions for Excel Sheet Column Number.
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// Memory Usage: 158.5 MB, less than 40.00% of Dart online submissions for Excel Sheet Column Number.
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int titleToNumber(String columnTitle) {
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// Initialize the output result...
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int result = 0;
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// Traverse the whole list through the loop...
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for (int i = 0; i < columnTitle.length; i++) {
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// Process to get the excel sheet column number...
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result *= 26;
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result += columnTitle[i].codeUnitAt(0) - 'A'.codeUnitAt(0) + 1;
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}
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return result;
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}
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}
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class C {
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// Runtime: 693 ms, faster than 40.00% of Dart online submissions for Excel Sheet Column Number.
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// Memory Usage: 148.3 MB, less than 60.00% of Dart online submissions for Excel Sheet Column Number.
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int titleToNumber(String columnTitle) {
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return columnTitle.length == 0
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? 0
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: (columnTitle.codeUnitAt(columnTitle.length - 1) -
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'A'.codeUnitAt(0) +
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1) +
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26 *
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titleToNumber(columnTitle.substring(0, columnTitle.length - 1));
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}
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}
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class D {
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/*
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Idea:
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Similar to our decimal representation on base 10, the excel column title also has similar representation but with base 26.
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In deciaml representation, for example, 123 would mean 1x10^2 + 2x10^1 + 3x10^0
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In excel column title, for example, ABC would mean 1x26^2 + 2x26^1 + 3x26^0
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We can use charCodeAt to convert letter to number, but it is offset by 64, so we need to subtract 64.
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Then we can use the representation from above to find the sum
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*/
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// Time lImit Exceed
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int titleToNumber(String columnTitle) {
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int sum = 0;
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for (int i = 0; i < columnTitle.length; i++) {
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int letter2Num = columnTitle.codeUnitAt(i) - 64;
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sum = (sum + pow(26, columnTitle.length - 1 - i) * letter2Num).toInt();
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}
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return sum;
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}
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}
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class E {
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// Runtime: 726 ms, faster than 20.00% of Dart online submissions for Excel Sheet Column Number.
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// Memory Usage: 148.7 MB, less than 60.00% of Dart online submissions for Excel Sheet Column Number.
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int titleToNumber(String columnTitle) {
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int ans = 0;
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for (int i = 0; i < columnTitle.length; i++) {
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ans *= 26;
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int c = columnTitle.codeUnitAt(i);
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int n = (c - 'A'.codeUnitAt(0) + 1);
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ans += n;
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}
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return ans;
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}
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}

‎ExcelSheetColumnNumber/excel_sheet_colum_number.dart.md

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# 🔥 Excel Sheet Column Number 🔥 || 5 Solutions || Simple Fast and Easy || with Explanation
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## Working Solutions
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### Solution - 1
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```dart
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class Solution {
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// Runtime: 656 ms, faster than 60.00% of Dart online submissions for Excel Sheet Column Number.
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// Memory Usage: 158.5 MB, less than 40.00% of Dart online submissions for Excel Sheet Column Number.
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int titleToNumber(String columnTitle) {
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// Initialize the output result...
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int result = 0;
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// Traverse the whole list through the loop...
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for (int i = 0; i < columnTitle.length; i++) {
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// Process to get the excel sheet column number...
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result *= 26;
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result += columnTitle[i].codeUnitAt(0) - 'A'.codeUnitAt(0) + 1;
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}
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return result;
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}
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}
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```
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### Solution - 2
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```dart
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class Solution {
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// Runtime: 693 ms, faster than 40.00% of Dart online submissions for Excel Sheet Column Number.
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// Memory Usage: 148.3 MB, less than 60.00% of Dart online submissions for Excel Sheet Column Number.
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int titleToNumber(String columnTitle) {
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return columnTitle.length == 0
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? 0
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: (columnTitle.codeUnitAt(columnTitle.length - 1) -
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'A'.codeUnitAt(0) +
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1) +
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26 *
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titleToNumber(columnTitle.substring(0, columnTitle.length - 1));
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}
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}
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```
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### Solution - 3
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```dart
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class Solution {
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// Runtime: 726 ms, faster than 20.00% of Dart online submissions for Excel Sheet Column Number.
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// Memory Usage: 148.7 MB, less than 60.00% of Dart online submissions for Excel Sheet Column Number.
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int titleToNumber(String columnTitle) {
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int ans = 0;
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for (int i = 0; i < columnTitle.length; i++) {
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ans *= 26;
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int c = columnTitle.codeUnitAt(i);
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int n = (c - 'A'.codeUnitAt(0) + 1);
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ans += n;
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}
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return ans;
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}
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}
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```
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## Time Limit Exceeded
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### Solution - 1 TLC
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```dart
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class Solution {
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// Time Limit exceeds
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int titleToNumber(String columnTitle) {
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int sum = 0;
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for (String ch in columnTitle.split("")) {
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int diff = ch.codeUnitAt(0) - ('A'.codeUnitAt(0) - 1);
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sum = sum * 26 + diff;
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}
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return sum;
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}
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}
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```
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### Solution - 2 TLC
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Idea:
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Similar to our decimal representation on base 10, the excel column title also has similar representation but with base 26.
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In decimal representation, for example, 123 would mean 1x10^2 + 2x10^1 + 3x10^0
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In excel column title, for example, ABC would mean 1x26^2 + 2x26^1 + 3x26^0
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We can use charCodeAt to convert letter to number, but it is offset by 64, so we need to subtract 64.
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Then we can use the representation from above to find the sum
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```dart
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class Solution {
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int titleToNumber(String columnTitle) {
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int sum = 0;
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for (int i = 0; i < columnTitle.length; i++) {
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int letter2Num = columnTitle.codeUnitAt(i) - 64;
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sum = (sum + pow(26, columnTitle.length - 1 - i) * letter2Num).toInt();
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}
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return sum;
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}
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}
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```

‎ExcelSheetColumnNumber/excel_sheet_colum_number.go

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package main
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import (
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"math"
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"strings"
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)
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func titleToNumber(columnTitle string) int {
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result := 0.0
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s := strings.ToLower(columnTitle)
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size := len(s)
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for i := 0; i < size; i++ {
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num := s[i] % 96
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n := size - 1 - i
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result += math.Pow(float64(26), float64(n)) * float64(num)
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}
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return int(result)
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}

‎README.md

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- [Majority Element](MajorityElement/majority_element.dart)
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- [The Skyline Problem](TheSkylineProblem/the_skyline_problem.dart)
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- [Two Sum III - Data Structure Design](TwoSum-III-DataStructureDesign/two_sum_III_data_structure_design.dart)
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- [Excel Sheet Column Number](ExcelSheetColumnNumber/excel_sheet_colum_number.dart)
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## Reach me via
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