Created
January 5, 2017 22:38
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Chipmunks Career Week Algo Problem 2
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| # Write a function that takes a string as input and reverse only the vowels of a string. | |
| # | |
| # Example 1: | |
| # Given s = "hello", return "holle". | |
| # | |
| # Example 2: | |
| # Given s = "leetcode", return "leotcede". | |
| # | |
| # Note: | |
| # The vowels does not include the letter "y". | |
| # pseudocode | |
| # have two pointers, one starting at the beginning of the string, one at the end | |
| # until the two pointers are pointing at the same index, | |
| # start iterating forwards through the string until hit a vowel | |
| # when hit vowel, start iterating backwards through the string until also hit a vowel | |
| # if this happens, then swap the two indices and continue advancing the first pointer | |
| # big O analysis | |
| # time complexity O(n) | |
| # space complexity O(1) | |
| def reverse_vowels(str) | |
| vowels = %w(a e i o u) | |
| forwards_pointer = 0 | |
| backwards_pointer = str.length - 1 | |
| while forwards_pointer < backwards_pointer | |
| if !vowels.include?(str[forwards_pointer]) | |
| forwards_pointer += 1 | |
| next | |
| end | |
| if !vowels.include?(str[backwards_pointer]) | |
| backwards_pointer -= 1 | |
| next | |
| end | |
| preceding_vowel = str[forwards_pointer] | |
| str[forwards_pointer] = str[backwards_pointer] | |
| str[backwards_pointer] = preceding_vowel | |
| forwards_pointer += 1 | |
| backwards_pointer -= 1 | |
| end | |
| str | |
| end | |
| p reverse_vowels("hello") |
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