Leetcode: Excel Sheet Column Number-优快云博客

本文详细解析了将Excel表格中列名转换为数值的算法，通过类似十进制到二十六进制的转换过程，实现了从字母列名到对应数值的高效映射。

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Problem:

Given a column title as appear in an Excel sheet, return its corresponding column number.

For example:

    A -> 1
    B -> 2
    C -> 3
    ...
    Z -> 26
    AA -> 27
    AB -> 28

Idea: It is like a conversion of number based on 26 to number based on 10.

My code:

public class Solution {
    public int titleToNumber(String s) {
        int result = 0;
        int power = 0;
        for (int i = s.length() - 1; i >= 0; i--) {
            int num = charToInt(s.charAt(i));
            result = result + caculate(num,power);
            power++;
        }
        return result;
  
        
    }
public int charToInt(char c) {
    	int result = 0;
        switch (c) {
        case 'A':
        	result = 1;
        	break;
        case 'B':
        	result = 2;
        	break;
        case 'C':
        	result = 3;
        	break;
        case 'D':
        	result = 4;
        	break;
        case 'E':
        	result = 5;
        	break;
        case 'F':
        	result = 6;
        	break;
        case 'G':
        	result = 7;
        	break;
        case 'H':
        	result = 8;
        	break;
        case 'I':
        	result = 9;
        	break;
        case 'J':
        	result = 10;
        	break;
        case 'K':
        	result = 11;
        	break;
        case 'L':
        	result = 12;
        	break;
        case 'M':
        	result = 13;
        	break;
        case 'N':
        	result = 14;
        	break;
        case 'O':
        	result = 15;
        	break;
        case 'P':
        	result = 16;
        	break;
        case 'Q':
        	result = 17;
        	break;
        case 'R':
        	result = 18;
        	break;
        case 'S':
        	result = 19;
        	break;
        case 'T':
        	result = 20;
        	break;
        case 'U':
        	result = 21;
        	break;
        case 'V':
        	result = 22;
        	break;
        case 'W':
        	result = 23;
        	break;
        case 'X':
        	result = 24;
        	break;
        case 'Y':
        	result = 25;
        	break;
        case 'Z':
        	result = 26;
        	break;
       
        }
        return result;
    } 
    public int caculate (int num, int power) {
        int base = 1;
        while (power >= 1) {
            base = base * 26;
            power--; 
        }
        return num * base;
    }
}

Other's code that is better and cleaner:

int result = 0;
for (int i = 0; i < s.length(); result = result * 26 + (s.charAt(i) - 'A' + 1), i++);
return result;