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Question
Formatted question description: https://leetcode.ca/all/344.html
Write a function that reverses a string. The input string is given as an array of characters s
.
You must do this by modifying the input array in-place with O(1)
extra memory.
Example 1:
Input: s = ["h","e","l","l","o"] Output: ["o","l","l","e","h"]
Example 2:
Input: s = ["H","a","n","n","a","h"] Output: ["h","a","n","n","a","H"]
Constraints:
1 <= s.length <= 105
s[i]
is a printable ascii character.
Algorithm
Go from both ends to the middle while swapping characters on both sides.
Code
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public class Reverse_String { class Solution { public void reverseString(char[] s) { int l = 0; int r = s.length - 1; while (l < r) { char tmp = s[l]; s[l] = s[r]; s[r] = tmp; l++; r--; } } } class Solution_cheat { public String reverseString(String input) { StringBuilder s = new StringBuilder(input); s.reverse(); return s.toString(); } } } ############ class Solution { public void reverseString(char[] s) { for (int i = 0, j = s.length - 1; i < j; ++i, --j) { char t = s[i]; s[i] = s[j]; s[j] = t; } } }
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// OJ: https://leetcode.com/problems/reverse-string/ // Time: O(N) // Space: O(1) class Solution { public: void reverseString(vector<char>& s) { int i = 0, j = s.size() - 1; while (i < j) swap(s[i++], s[j--]); } };
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class Solution: def reverseString(self, s: List[str]) -> None: """ Do not return anything, modify s in-place instead. """ s[:] = s[::-1] ############ class Solution(object): def reverseString(self, s): """ :type s: str :rtype: str """ return s[::-1]
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func reverseString(s []byte) { for i, j := 0, len(s)-1; i < j; i, j = i+1, j-1 { s[i], s[j] = s[j], s[i] } }
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/** * @param {character[]} s * @return {void} Do not return anything, modify s in-place instead. */ var reverseString = function (s) { for (let i = 0, j = s.length - 1; i < j; ++i, --j) { [s[i], s[j]] = [s[j], s[i]]; } };
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impl Solution { pub fn reverse_string(s: &mut Vec<char>) { let n = s.len(); let mut l = 0; let mut r = n - 1; while l < r { s.swap(l, r); l += 1; r -= 1; } } }