反转字符串

编写一个函数，其作用是将输入的字符串反转过来。

示例 1:

输入: "hello"
输出: "olleh"

示例 2:

输入: "A man, a plan, a canal: Panama"
输出: "amanaP :lanac a ,nalp a ,nam

public class Solution {
    public string ReverseString(string s) {
        char[] result = new char[s.Length];
        int left = 0;
        int right = s.Length-1;
        while(left <= right)
        {
            result[left] = s[right];
            result[right] = s[left];
            left++;
            right--;
        }
        return new string(result);
    }
}

 

public class Solution {
    public string ReverseString(string s) {
        var i = 0;
        var j = s.Length - 1;
        var charArray = s.ToCharArray();
        char temp;
        while (i < j) {
            temp = charArray[i];
            charArray[i] = charArray[j];
            charArray[j] = temp;
            ++i;
            --j;
        }
        return new string(charArray);
    }
}

 用时较长

public class Solution {
    public string ReverseString(string s) {
        /*
        string str="";
        for(int i=s.Length-1;i>=0;i--){
            str+=s[i];
        }
        return str;
        */
         StringBuilder sb=new StringBuilder(s.Length);
        for(int i=s.Length-1;i>=0;i--){
            sb.Append(s[i]);
        }
        return sb.ToString();
    }
}