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This approach involves treating each character of the column title string as a digit in a base-26 number system. We iterate over the string from left to right, calculating its contribution to the overall number at each step by multiplying with an appropriate power of 26.
Time Complexity: O(n), where n is the length of the column title.
Space Complexity: O(1), as no additional space is used that scales with input size.
1#include <stdio.h>
2
3int titleToNumber(char * columnTitle) {
4 int result = 0;
5 while (*columnTitle) {
6 result = result * 26 + (*columnTitle - 'A' + 1);
7 columnTitle++;
8 }
9 return result;
10}
11
12int main() {
13 char columnTitle[] = "AB";
14 printf("%d\n", titleToNumber(columnTitle));
15 return 0;
16}We initialize a result variable to 0. As we iterate over each character of the column title, we multiply the current result by 26 and add the integer value of the current character (adjusted by 'A' to get 1-based index). This mimics adding a digit in a base-26 system.
This approach uses recursion to compute the column number. Starting from the first character, the function recursively converts the rest of the string and adds the current character's contribution by treating it as a digit in a 26-based number system. This implements a divide-and-conquer strategy.
Time Complexity: O(n)
Space Complexity: O(n), due to recursion stack space.
1
This JavaScript solution uses a recursive function to decompose the problem by handling each character as a separate call and summing up their contributions in the calculation.