Java代码练习2_javapackage com.task4.demo; import java.util.scann

day29

年会抽奖

思路：年会抽奖

import java.util.Scanner;
public class Main{
    public static float fac(int n){
        if(n == 0)
            return 1;
        return n * fac(n - 1);
    }
    public static float count(int n) {
        if(n == 1){
            return 0;
        }
        if(n == 2){
            return 1;
        }else{
            return (n - 1) * (count(n - 1) + count(n - 2));
        }
    }
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNextInt()){
            int n = sc.nextInt();
            float ret =  count(n) / fac(n) * 100;
            System.out.println(String.format("%.2f", ret) + "%");
        }
    }
}
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数字和为sum的方法数

思路：动态规划
数字和为sum的方法数

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        int n = cin.nextInt();
        int m = cin.nextInt();
        int arr[] = new int[n+1];
                //代表你使用前i个数组组成j的最大组合数
        long dp[][] = new long[n + 1][m + 1];
        for (int i = 1; i <= n; i++) {
            arr[i] = cin.nextInt();
        }
        for (int i = 0; i < m; i++) {
            dp[0][i] = 0;
        }
        //注意，你的dp[0][0]一定要是1，否则会出错
        for (int i = 0; i < n; i++) {
            dp[i][0] = 1;
        }
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= m; j++) {
                if (arr[i] <= j) {
                    dp[i][j] = dp[i - 1][j] + dp[i - 1][j - arr[i]];
                } else {
                    dp[i][j] = dp[i - 1][j];
                }
            }
        }
        System.out.println(dp[n][m]);
    }
}
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day30

奇偶校验

思路：这一题里面将数字和字母统一看成是char类型的，所以数字3实际存储时为ASCII码中的‘3’，其十进制表示是51，转化为二进制表示就是0110011，取最高位为奇校验位，校验位为1，所以校验后的二进制数为10110011，字母同理。故本题只需将输入的字符减去‘\0’得到字符的十进制表示，再将其转化为七位二进制数加上一位校验位输出即可。

import java.util.Scanner;
public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            String s = sc.next();
            char[] arr = s.toCharArray();
            for(char c : arr){
                String s1 = Integer.toBinaryString(c);
                String s2 = String.format("%07d", Integer.parseInt(s1));
                int count = 0;
                for(int i = 0; i < 7; i++){
                    if(s2.charAt(i) == '1')
                        count++;
                }
                System.out.println(count % 2 == 0 ? "1" + s2 : "0" + s2);
            }
        }
    }
}
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大整数排序

import java.util.Scanner;
import java.util.ArrayList;
import java.util.Collections;
import java.math.BigInteger;
public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            ArrayList<BigInteger> list = new ArrayList<BigInteger>();
            int n = sc.nextInt();
            for(int i = 0; i < n; i++){
                list.add(new BigInteger(sc.next()));
            }
            Collections.sort(list);
            for(BigInteger i : list){
                System.out.println(i);
            }
        }
    }
}
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day31

import java.util.Scanner;
public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            String s = sc.nextLine();
            String[] arr = s.split(" ");
            for(int i = arr.length - 1; i >= 0; i--){
                if(i != 0){
                    System.out.print(arr[i] + " ");
                }else{
                    System.out.print(arr[i]);
                }
            }
        }
    }
}
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简单错误记录：


看下大佬的代码，膜拜。。

import java.util.*;
public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        Map<String, Integer> map = new LinkedHashMap<>();
        while(sc.hasNextLine()){
            String s = sc.nextLine();
            String[] arr = s. split(" ");
            String key = arr[0].substring(arr[0].lastIndexOf("\\") + 1) + " " + arr[1];
            map.put(key, map.containsKey(key) ? map.get(key) + 1 : 1);
        }
        List<Map.Entry<String, Integer>> list = new ArrayList<>(map.entrySet());
        Collections.sort(list, new Comparator<Map.Entry<String, Integer>>(){
            @Override
            public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2){
                return o2.getValue().compareTo(o1.getValue());
            }
        });
        for(int i = 0; i < 8; i++){
            String[] arr1 = list.get(i).getKey().split(" ");
            if(arr1[0].length() > 16){
                arr1[0] = arr1[0].substring(arr1[0].length() - 16);
            }
            System.out.println(arr1[0] + " " + arr1[1] + " " + list.get(i).getValue());
        }
    }
}
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day32

在霍格沃茨找零钱

import java.util.Scanner;
public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            String[] arr = sc.nextLine().split(" ");
            String[] s1 = arr[0].split("\\.");
            String[] s2 = arr[1].split("\\.");
            int[] a1 = new int[3];
            int[] a2 = new int[3];
            for(int i = 0; i < 3; i++){
                a1[i] = Integer.parseInt(s1[i]);
                a2[i] = Integer.parseInt(s2[i]);
            }
            int m1 = ((a1[0] * 17 + a1[1]) * 29) + a1[2];
            int m2 = ((a2[0] * 17 + a2[1]) * 29) + a2[2];
            int diff = m2 - m1;
            if(m2 < m1){
                System.out.print("-");
                diff = -diff;
            }
            System.out.println(diff / (17 * 29) + "." + (diff % (17 * 29)) / 29 + "." + (diff % (17 * 29)) % 29);
        }
    }
}
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思路：https://blog.csdn.net/huzhigenlaohu/article/details/51779365

import java.util.*;

public class Count2 {
    public int countNumberOf2s(int n) {
        int count = 0;
        for(int i = 1; i <= n; i *= 10){
            int a = n / i;
            int b = n % i;
            count += (a + 7) / 10 * i + ((a % 10 == 2) ? b + 1 : 0);
        }
        return count;
    }
}
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day33

锤子剪刀布

链接：https://www.nowcoder.com/questionTerminal/79db907555c24b15a9c73f7f7d0e2471
来源：牛客网

public class B1008RockScissorsPaper {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
 
        Model mA = new Model();
        Model mB = new Model();
 
        for (int i = 0; i < N; i++) {
            String a = sc.next();
            String b = sc.next();
            judge(a, b, mA, mB);
        }
 
        System.out.println(mA.win + " " + mA.tie + " " + mA.lose);
        System.out.println(mB.win + " " + mB.tie + " " + mB.lose);
        System.out.println(getMostGen(mA.map) + " " + getMostGen(mB.map));
    }
 
    public static void judge(String a, String b, Model mA,
                             Model mB) {
        if (a.equals("C")) {
            if (b.equals("C")) {
                mA.tie++;
                mB.tie++;
            } else if (b.equals("J")) {
                mA.win++;
                mB.lose++;
                mA.map.put("C", mA.map.get("C") + 1);
            } else {
                mA.lose++;
                mB.win++;
                mB.map.put("B", mA.map.get("B") + 1);
            }
        } else if (a.equals("J")) {
            if (b.equals("C")) {
                mA.lose++;
                mB.win++;
                mB.map.put("C", mA.map.get("C") + 1);
            } else if (b.equals("J")) {
                mA.tie++;
                mB.tie++;
            } else {
                mA.win++;
                mB.lose++;
                mA.map.put("J", mA.map.get("J") + 1);
            }
        } else {
            if (b.equals("C")) {
                mA.win++;
                mB.lose++;
                mA.map.put("B", mA.map.get("B") + 1);
            } else if (b.equals("J")) {
                mA.lose++;
                mB.win++;
                mB.map.put("J", mA.map.get("J") + 1);
            } else {
                mA.tie++;
                mB.tie++;
            }
        }
    }
 
    public static String getMostGen(Map<String, Integer> map) {
        if (map.get("C") >= map.get("J")) {
            if (map.get("C") > map.get("B")) {
                return "C";
            } else {
                return "B";
            }
        } else {
            if (map.get("J") > map.get("B")) {
                return "J";
            } else {
                return "B";
            }
        }
    }
 
    static class Model {
        int win;
        int tie;
        int lose;
        Map<String, Integer> map;
 
        Model() {
            map = new HashMap<>();
            map.put("B", 0);
            map.put("C", 0);
            map.put("J", 0);
        }
    }
}
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96

import java.util.*;

public class GoUpstairs {
    //Fibonacci sequence f(n) = f(n-1)+f(n-2)+f(n-3); And f(1)=1,f(2)=2,f(3)=4
    public int countWays(int n) {
        int[] arr = {1, 2, 4};
        if(n <= 0)
            return 0;
        else if(n <= 3)
            return arr[n - 1];
        else{
            for(int i = 4; i <= n; i++){
                int tmp = ((arr[0] + arr[1]) % 1000000007 + arr[2]) % 1000000007;
                arr[0] = arr[1];
                arr[1] = arr[2];
                arr[2] = tmp;
            }
        }
        return arr[2];
    }
}
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day34

旧键盘：

import java.util.Scanner;
public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            String s1 = sc.nextLine().toUpperCase();
            String s2 = sc.nextLine().toUpperCase();
            StringBuilder ret = new StringBuilder();
            for(int i = 0; i < s1.length(); i++){
                if(s2.indexOf(s1.charAt(i)) == -1 && ret.toString().indexOf(s1.charAt(i)) == -1)
                    ret.append(s1.charAt(i));
            }
            System.out.println(ret);
        }
    }
}
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import java.util.Scanner;
import java.math.*;
public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            double[] arr = new double[6];
            for(int i = 0; i < 6; i++){
                arr[i] = (double)sc.nextInt();
            }
            double r = Math.sqrt((arr[3] - arr[0]) * (arr[3] - arr[0]) + (arr[4] - arr[1]) * (arr[4] - arr[1]) + (arr[5] - arr[2]) * (arr[5] - arr[2]));
            double v = 4.0 / 3.0 * Math.acos(-1.0) * r * r * r;
            System.out.printf("%.3f ", r);
            System.out.printf("%.3f", v);
            System.out.println();
        }
    }
}
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day35

风口的猪，中国牛市

import java.math.*;
public class Solution {
    /**
     * 计算你能获得的最大收益
     * 
     * @param prices Prices[i]即第i天的股价
     * @return 整型
     */
    public static int getMaxDiff(int[] prices, int left, int right){
        if(left >= right)
            return 0;
        int ret = 0;
        for(int i = left; i <= right; i++){
            for(int j = left; j < i; j++){
                ret = Math.max(ret, prices[i] - prices[j]);
            }
        }
        return ret;
    }
    public int calculateMax(int[] prices) {
        if(prices == null || prices.length < 2)
            return 0;
        int ret = 0;
        for(int i = 1; i < prices.length; i++){
            ret = Math.max(ret, getMaxDiff(prices, 0, i) + getMaxDiff(prices, i + 1, prices.length - 1));
        }
        return ret;
    }
}
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day36

import java.util.*;
public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            char[] arr = sc.nextLine().toCharArray();
            int[] ret = new int[256];
            for(char c : arr){
                ret[c]++;
            }
            for(int i = 'A'; i <= 'Z'; i++){
                System.out.println((char)i + ":" + ret[i]);
            }
        }
    }
}
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day37

import java.util.*;
public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            int n = sc.nextInt();
            ArrayList<Integer> list = new ArrayList<>();
            for(int i = 0; i < n; i++){
                int op = sc.nextInt();
                int l = sc.nextInt();
                if(op == 1){
                    list.add(l);
                }else{
                    int index = list.indexOf(l);
                    list.remove(index);
                }
                if(list.size() < 3){
                    System.out.println("No");
                }else{
                    Collections.sort(list, Collections.reverseOrder());
                    int max = list.get(0);
                    int sum = 0;
                    for(int j = 1; j < list.size(); j++){
                        sum += list.get(j);
                    }
                    if(sum > max){
                        System.out.println("Yes");
                    }else{
                        System.out.println("No");
                    }
                }
            }
        }
    }
}
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35

地下迷宫

import java.util.Iterator;
import java.util.LinkedList;
import java.util.Scanner;
public class Main{
    
    static int n, m, maxRemainEnergy = 0;
    static int[][] map;
    static String path = "";
    static boolean flag = false;
    static LinkedList<String> list = new LinkedList<>();
    
    public static void runMap(int x, int y, int energy){
        if(x < 0 || y < 0 || x >= n || y >= m || energy < 0 || map[x][y] != 1)
            return;
        else{
            list.offer("[" + x + "," + y + "]");
            map[x][y] = 0;
            if(x == 0 && y == m - 1){
                if(energy >= maxRemainEnergy){
                    maxRemainEnergy = energy;
                    updatePath();
                }
                map[x][y] = 1;
                list.removeLast();
                flag = true;
                return;
            }
            runMap(x, y + 1, energy - 1);
            runMap(x + 1, y, energy);
            runMap(x - 1, y, energy - 3);
            runMap(x, y - 1, energy - 1);
            map[x][y] = 1;
            list.removeLast();
        }
    }
    
    public static void updatePath(){
        StringBuilder sb = new StringBuilder();
        Iterator<String> iterator = list.iterator();
        while(iterator.hasNext()){
            sb.append(iterator.next() + ",");
        }
        if(sb.length() > 0){
            sb.deleteCharAt(sb.length() - 1);
        }
        path = sb.toString();
    }
    
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            n = sc.nextInt();
            m = sc.nextInt();
            int p = sc.nextInt();
            map = new int[n][m];
            for(int i = 0; i < n; i++){
                for(int j = 0; j < m; j++){
                    map[i][j] = sc.nextInt();
                }
            }
            
            runMap(0, 0, p);
            
            if(!flag){
                System.out.println("Can not escape!");
            }else{
                System.out.println(path);
            }
        }
    }
}
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day38