344. Reverse String

Discuss Pick One

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Write a function that takes a string as input and returns the string reversed.

Example:
Given s = "hello", return "olleh".

注意runtime error ！！如果只是遍历会超时  下面注释掉的就是超时的方法

class Solution {
    public String reverseString(String s) {
        // if(s==null||s.length()==0)
        //     return "";
        // String res ="";
        // for(int i=s.length()-1;i>=0;i--){
        //     res = res+s.charAt(i);
        // }
        // return res;
        
        char[] arr = s.toCharArray();
        int len=s.length();
        for(int i=0;i<len/2;i++){
            char temp = arr[i];
            arr[i]=arr[len-1-i];
            arr[len-1-i]=temp;
        }
        return new String(arr);

    }
}