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This approach utilizes the built-in function available in standard libraries of most programming languages to convert strings to lowercase. Such functions are usually optimized and provide a direct solution to the problem by iterating over each character in the string and converting it to its lowercase equivalent if it's uppercase.
Time Complexity: O(n), where n is the length of the string, as we iterate through the string once.
Space Complexity: O(1), as the conversion is done in-place without any additional space.
1#include <stdio.h>
2#include <string.h>
3#include <ctype.h>
4
5char* toLowerCase(char* s) {
6 for (int i = 0; s[i] != '\0'; i++) {
7 s[i] = tolower(s[i]);
8 }
9 return s;
10}
11
12int main() {
13 char s[] = "Hello";
14 printf("%s\n", toLowerCase(s));
15 return 0;
16}In this C example, the tolower() function from ctype.h is used. It converts each character of the string to lowercase in-place if it is an uppercase letter.
This approach manually converts each character by examining its ASCII value. If a character is uppercase (between 65, 'A', and 90, 'Z'), we add 32 to convert it to its lowercase counterpart (between 97, 'a', and 122, 'z'). This method ensures you understand converting characters without relying on the language built-in functions.
Time Complexity: O(n), due to iterating through each character.
Space Complexity: O(1), since the conversion happens in-place.
1
This Java code converts the string to a character array and modifies each uppercase letter by adding 32, then constructs a new string from the modified character array.