Leetcode 344. Reverse String--输入字符数组，倒序输出

Write a function that reverses a string. The input string is given as an array of characters char[].

Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.

You may assume all the characters consist of printable ascii characters.

 

Example 1:

Input: ["h","e","l","l","o"]
Output: ["o","l","l","e","h"]

Example 2:

Input: ["H","a","n","n","a","h"]
Output: ["h","a","n","n","a","H"]

 

package com.string;

/**
 * Title:
 *
 * @Author
 * @CreateTime 2019/6/15 15:32
 */
public class Leetcode_344_ReverseString {
    /**
     * for循环写不写均能AC
     * <p>
     * 不写for循环时：
     * Runtime: 1 ms, faster than 100.00% of Java online submissions for Reverse String.
     * Memory Usage: 47.7 MB, less than 68.18% of Java online submissions for Reverse String.     * <p>
     * 写for循环时：
     * Runtime: 107 ms, faster than 12.11% of Java online submissions for Reverse String.
     * Memory Usage: 65.5 MB, less than 5.01% of Java online submissions for Reverse String.
     *
     * @param s
     */
    public void reverseString2(char[] s) {
        int i = 0, j = s.length - 1;
        char temp;
        while (i < j) {
            temp = s[i];
            s[i] = s[j];
            s[j] = temp;
            i++;
            j--;
        }

        for (int k = 0; k < s.length; k++) {
            if (k == 0) {
                System.out.print("[");
            }
            if (k != s.length - 1) {
                System.out.print("\"" + s[k] + "\",");
            } else {
                System.out.print("\"" + s[k] + "\"]");
            }
        }//for
    }//reverseString


    /**
     * Runtime: 1 ms, faster than 100.00% of Java online submissions for Reverse String.
     * Memory Usage: 47.2 MB, less than 68.80% of Java online submissions for Reverse String.
     *
     * @param s
     */
    public void reverseString(char[] s) {
        for (int i = 0; i < s.length / 2; i++) {
            char temp = s[i];
            s[i] = s[s.length - 1 - i];
            s[s.length - 1 - i] = temp;
        }
    }

    public static void main(String[] args) {
        Leetcode_344_ReverseString object = new Leetcode_344_ReverseString();
        object.reverseString(new char[]{'h', 'e', 'l', 'l', 'o'});
    }
}