Brooke

一、題目

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.

 

二、程式作法

public class Solution
{
    public void ReverseString(char[] s)
    {
        //System.Array.Reverse(s);

        int left = 0;
        int right = s.Length - 1;

        while (left < right)
        {
            char temp = s[left];
            s[left] = s[right];
            s[right] = temp;

            left++;
            right--;
        }
    }
}

 

三、思路筆記

題目要的結果為將一陣列的排列做反轉，兩種作法，

第一種作法，我們知道第一個元素會與倒數第一個做交換，第二個元素會與倒數第二個做交換，

所以也是宣告左右兩指標來逼近中間，進而完成反轉需求。

第二種作法，直接呼叫 System.Array.Reverse() 方法來幫我們處理到好。