CareerCup 150

C.C 1.2

/**
 * 1.2 Implement a function void reverse(char* str) in C or C++ which reverses a
 * null-terminated string.
 *
 * @author Jiateng
 */
public class CC1_2 {

    //Time O(n), Space O(n)
    public static String reverse1(String target) {

        StringBuilder result = new StringBuilder();
        //directly add from the end to the start
        for (int i = target.length() - 1; i >= 0; i--) {
            result.append(target.charAt(i));
        }

        return result.toString();
    }

    //Time O(n), Space O(1)
    public static String reverse2(String target) {
        //make an array
        char[] array = target.toCharArray();
        //start
        int left = 0;
        //end
        int right = array.length - 1;

        while (left < right) {
            //swap
            char temp = array[right];
            array[right] = array[left];
            array[left] = temp;
            //move from both start and end to the middle
            left++;
            right--;
        }

        return String.valueOf(array);
    }

    public static void main(String[] args) {
        String target = "sodufhosdg";

        System.out.println(reverse1(target));
        System.out.println(reverse2(target));
    }
}

In StringBuffer type， there is a reverse() method to fast reverse the stringBuffer.