科大讯飞笔试 AK

第一题：倒序输出即可

public class App {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        for (int i = n; i >= 1; i--)
            System.out.print(i+" ");
    }
}

第二题：一次遍历：

public class App {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt(), k = sc.nextInt();
        String s = sc.next();
        if (s.length() == 1) {
            System.out.println(k);
            return;
        }
        int i = 1;
        for (i = 1; i < s.length(); i++) {
            int diff = s.charAt(i) - s.charAt(i - 1);
            k -= diff;
            if (k < 0)
                break;
        }
        System.out.println(i == s.length() ? k : -1);
    }
}

第三题：记录重复长度

public class App {

    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] arr1 = new int[n], arr2 = new int[n];
        Map<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < n; i++)
            arr1[i] = sc.nextInt();
        for (int i = 0; i < n; i++) {
            arr2[i] = sc.nextInt();
            map.put(arr2[i], i);
        }
        long sum = (long) n * (n + 1);
        int cnt = 1;
        for (int i = 0; i < arr1.length; i++) {
            int idx = map.get(arr1[i]);
            if (idx < n - 1 && i < n - 1 && arr2[idx + 1] == arr1[i + 1]) {
                cnt++;
            } else {
                sum -= (long) (cnt + 1) * cnt / 2;
                cnt = 1;
            }
        }
        System.out.println(sum);
    }
}