题解 | #字符串变形#

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Solution {

    public String trans(String s, int n) {
        // write code here
        if (s == null || s.length() < 1 || n < 1) {
        }
        char[] arr = s.toCharArray();
        for (int i = 0; i < n; i++) {
            if (arr[i] >= 'a' && arr[i] <= 'z') {
                arr[i] = (char) (arr[i] - 'a' + 'A');
            } else if (arr[i] >= 'A' && arr[i] <= 'Z') {
                arr[i] = (char) (arr[i] - 'A' + 'a');
            }
        }
        reverse(arr, 0, n - 1);
        for (int i = 0; i < n; i++) {
            int j = i;
            while (j < n && arr[j] != ' ') {
                j++;
            }
            if (j != i) {
                reverse(arr, i, j - 1);
            }
            i = j;
        }
        return new String(arr);
    }

    private void reverse(char[] arr, int i, int j) {
        while (i < j) {
            char tmp = arr[i];
            arr[i] = arr[j];
            arr[j] = tmp;
            i++;
            j--;
        }
    }
}