九度 1402 特殊的数

普通的方法：

package com.wangzhu.njupt;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.StreamTokenizer;

/**
 * 由于输入的数在1~100000之间，故只需要开个100000大小的数组，判断其是否存在即可
 * 
 * @ClassName: Main1402
 * @Description: TODO
 * @author 王竹
 * @date 2014-10-3 下午5:21:31
 * 
 */
public class Main1402 {

    private static final int LEN = 1000001;

    /**
     * @param args
     * @throws IOException
     */
    public static void main(String[] args) throws IOException {
        // System.setIn(new FileInputStream("data.in"));
        // 输入优化
        StreamTokenizer in = new StreamTokenizer(new BufferedInputStream(
                System.in));
        // Scanner cin = new Scanner(new BufferedInputStream(System.in));
        // while (cin.hasNext()) {
        while (in.nextToken() != StreamTokenizer.TT_EOF) {
            int[] arr = new int[LEN];
            // int n = cin.nextInt();
            int n = (int) in.nval;
            int m = -1;
            for (int i = 0; i < n; i++) {
                // m = cin.nextInt();
                in.nextToken();
                m = (int) in.nval;
                arr[m]++;
            }
            StringBuilder sb = new StringBuilder();
            int c = 0, index = 0;
            for (int i = 1; i < LEN; i++) {
                if (arr[i] == 1) {
                    if (index == 0) {
                        sb.append(i);
                        index = 1;
                    } else {
                        sb.append(" ").append(i);
                    }
                    c++;
                }
            }
            System.out.println(c);
            if (c > 0) {
                System.out.println(sb);
            }

        }
    }
}

位存储的方法：

package com.wangzhu.njupt;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StreamTokenizer;
import java.util.Scanner;

public class Main14022 {

    /**
     * 用位来存储数
     */
    private static final int LEN = (1000000 >> 3) + 10;
    /**
     * 用于模8，即与7
     */
    private static final int MASK = (1 << 3) - 1;
    /**
     * 要查的数的范围为1~1000000
     */
    private static final int SIZE = 1000001;

    /**
     * @param args
     * @throws IOException
     */
    public static void main(String[] args) throws IOException {
        // System.setIn(new FileInputStream("data.in"));
        // Scanner cin = new Scanner(new BufferedInputStream(System.in));
        // 输入优化
        StreamTokenizer in = new StreamTokenizer(new BufferedInputStream(
                System.in));
        // 输出优化
        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
        // while (cin.hasNext()) {
        while (in.nextToken() != StreamTokenizer.TT_EOF) {
            int[] arr = new int[LEN];
            int[] flag = new int[LEN];
            // int n = cin.nextInt();
            int n = (int) in.nval;
            for (int i = 0; i < n; i++) {
                // int m = cin.nextInt();
                in.nextToken();
                int m = (int) in.nval;
                // 其实是除以8
                int index = m >> 3;
                // 其实是模8
                int bit = m & MASK;
                if ((arr[index] & (1 << bit)) == 0) {
                    // 记录输入中的数
                    arr[index] |= (1 << bit);
                } else if ((flag[index] & (1 << bit)) == 0) {
                    // 记录输入多个同样的数
                    flag[index] |= (1 << bit);
                }
            }
            int cnt = 0;
            for (int i = 1; i < SIZE; i++) {
                int index = i >> 3;
                int bit = i & MASK;
                if ((arr[index] & (1 << bit)) != 0
                        && (flag[index] & (1 << bit)) == 0) {
                    // 判断是输入的数并且只输入了一次
                    // 记录这种数的个数
                    cnt++;
                }
            }
            StringBuilder sb = new StringBuilder();
            int j = 0;
            for (int i = 1; (i < SIZE) && (j < cnt); i++) {
                int index = i >> 3;
                int bit = i & MASK;
                if ((arr[index] & (1 << bit)) != 0
                        && (flag[index] & (1 << bit)) == 0) {
                    sb.append(i).append(" ");
                    j++;
                }
            }
            String ret = null;
            out.println(cnt);
            if (cnt > 0) {
                ret = sb.substring(0, sb.length() - 1);
                out.println(ret);
            }
            out.flush();
        }
    }
}

备注：

关于位运算的一些补充：

例如，

关于n/8，可以转化为n>>3。

关于n%8，可以转化为n&7，当然也已转化为n - (n>> 3)<<3。