题解 | #提取不重复的整数#

方法1:

/*
 * 解题思路: 通过LinkedHashSet去重 (直接打印就用HashSet了)
 */
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        char[] input = sc.nextLine().toCharArray();
        int len = input.length;
        HashSet<Integer> set = new HashSet();

        for (int i = len - 1; i >= 0; i--) {
            // char转int需要显示强转!
            if (set.contains((int)input[i])) {
                continue;
            }
            set.add((int)input[i]);
            System.out.print(input[i]);
        }
    }
}

方法2:

/*
 * 解题思路: 通过数组下标去重
 */
import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        char[] input = sc.nextLine().toCharArray();
        int len = input.length;
        int[] set = new int[10];

        for (int i = len - 1; i >= 0; i--) {
            // char转int需要显示强转, 而且我老是忘记减'0'
            int ch = (int)input[i] - '0';
            if (set[ch] == 1) {
                continue;
            }
            set[ch] = 1;
            System.out.print(ch);
        }
    }
}