leetcode[Reverse String]

解法一：

public class Solution {
    public String reverseString(String s) {
        StringBuilder sb = new StringBuilder(s);
        sb = sb.reverse();
        return sb.toString();
    }
}

解法二：

public class Solution {
	//递归做法
	public String reverseString(String s) {
		int length = s.length();
		if (length <= 1) return s;
		String leftStr = s.substring(0, length / 2);
		String rightStr = s.substring(length / 2, length);
		return reverseString(rightStr) + reverseString(leftStr);
	}
}

解法三：

public class Solution {
	public String reverseString(String s) {
		char[] c = s.toCharArray();
		for(int i = 0, j = c.length - 1; i < j; i++, j--){
			//从首尾开始，交换
			char t = c[i];
			c[i] = c[j];
			c[j] = t;
		}
		return new String(c);
	}
}