拼多多2018

1.有两个用字符串表示的非常大的大整数,算出他们的乘积，也是用字符串表示。不能用系统自带的大整数类型。

解析：大数相乘，模拟一下。

package pdd.nt;

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

/**
 * Created by cuijunyong on 2018/3/20.
 */
public class Mul {

  public static void main(String[] args) {
    Scanner cin = new Scanner(System.in);
    String a = cin.next();
    String b = cin.next();
    String c = mul(a, b);
    System.out.println(c);
  }

  private static String mul(String x, String y) {
    char[] a = x.toCharArray();
    char[] b = y.toCharArray();
    List<Long> c = new ArrayList();
    for(int i = a.length - 1; i >= 0; i--){
      long v = 0;
      for(int j = b.length - 1; j >= 0; j--){
        v += (a[i] - '0') * (b[j] - '0');
        int pos = b.length - 1 - j + (a.length - 1 - i);
        if(c.size() <= pos){
          c.add(v % 10);
        }else{
          v += c.get(pos);
          c.set(pos, v % 10);
        }
        v /= 10;
      }

      while (v > 0){
        c.add(v % 10);
        v /= 10;
      }

    }
    String str = "";
    for(int i = c.size() - 1; i >= 0; i-- ){
      str += c.get(i);
    }
    return str;
  }
}

2.六一儿童节，老师带了很多好吃的巧克力到幼儿园。每块巧克力j的重量为w[j]，对于每个小朋友i，当他分到的巧克力大小达到h[i] (即w[j]>=h[i])，他才会上去表演节目。老师的目标是将巧克力分发给孩子们，使得最多的小孩上台表演。可以保证每个w[i]> 0且不能将多块巧克力分给一个孩子或将一块分给多个孩子。

解析：一看就先想到了二分匹配，看了解析看到他们用的排序模拟也做出来了。

package pdd.nt;

import java.util.Scanner;

/**
 * Created by cuijunyong on 2018/3/20.
 */
public class day61 {

  private static Scanner cin = new Scanner(System.in);
  private static int n, m;
  private static int[] h,w;
  private static int[][] mp;
  private static int[] d;
  private static int[] v;

  public static void main(String[] args) {
    init();
    int ans = 0;
    for(int i = 0; i < n; i++){
      for(int j = 0; j < m; j++){
        v[j] = 0;
      }
      if(dfs(i)){
        ans ++;
      }
    }
    System.out.println(ans);
  }

  private static boolean dfs(int x){
    for(int i = 0; i < m; i++){
      if(v[i] == 0 && mp[x][i] == 1){
        v[i] = 1;
        if(d[i] == -1 || dfs(d[i])){
          d[i] = x;
          return true;
        }
      }
    }
    return false;
  }

  private static void init(){
    n = cin.nextInt();
    h = new int[n];
    for(int i = 0; i < n; i++){
      h[i] = cin.nextInt();
    }
    m = cin.nextInt();
    w = new int[m];
    for(int i = 0; i < m; i++){
      w[i] = cin.nextInt();
    }

    d = new int[m];
    for(int i = 0; i < m; i++){
      d[i] = -1;
    }

    v = new int[m];
    for(int i = 0; i < m; i++){
      v[i] = 0;
    }
    mp = new int[n][m];
    for(int i = 0; i < n; i++){
      for(int j = 0; j < m; j++){
        if(h[i] <= w[j]){
          mp[i][j] = 1;
        }
      }
    }

  }
}

 3.将1+3+3+4变成1+3*2+4

package pdd.cz;

/**
 * Created by cuijunyong on 2018/3/20.
 */
import java.util.*;

public class A {
  private static Map<Long, Integer> map = new HashMap<Long, Integer>();
  private static Set<Long> set = new HashSet<Long>();

  public static void main(String[] args) {
    Scanner cin = new Scanner(System.in);
    String str = cin.next();
    init(str);
  }

  private static void init(String str) {
    map.clear();
    set.clear();
    Long x = 0L;
    Long sum = 0L;
    str += "+";
    for(int i = 0; i < str.length(); i++){
      char c = str.charAt(i);
      if(c >= '0' && c <= '9'){
        x = x * 10 + c - '0';
      }else{
        Integer v = map.get(x);
        if(v == null){
          v = 0;
        }
        v++;
        map.put(x, v);
        set.add(x);
        sum += x;
        x = 0L;
      }
    }
    Object[] objects = set.toArray();
    long[] arr = new long[objects.length];
    for(int i = 0; i < objects.length; i++){
      arr[i] = (Long)objects[i];
    }
    Arrays.sort(arr);
    String ans = "";
    for(int i = 0; i < arr.length; i++){
      Long next = arr[i];
      if(i != 0){
        ans += "+";
      }
      ans += next + "*" + map.get(next);
    }
    System.out.println(ans);
    System.out.println(sum);
  }
}

4.坐出租车，每辆最多坐4个人，要求一队不能分开。

package pdd.cz;

/**
 * Created by cuijunyong on 2018/3/20.
 */
/*

6
1 2 4 3 3 2

*/
import java.util.*;

public class B {


  public static void main(String[] args) {
    Scanner cin = new Scanner(System.in);
    int N;
    N = cin.nextInt();
    int[] p = new int[N];
    int[] num = new int[5];
    for(int i = 0; i < 5; i++){
      num[i] = 0;
    }
    for(int i = 0; i < N; i++){
      p[i] = cin.nextInt();
      num[p[i]]++;
    }

    int ans;

    ans = num[4] + (num[2] + 1)/2;

    if(num[3] > num[1]){
      ans += num[1] + num[3] - num[1];
    }else{
      ans += num[3] + (num[1] - num[3] + 3)/4;
    }

    if(num[2] % 2 == 1 && (num[1] - num[3])%4 <= 2 && (num[1] - num[3])%4 > 0){
      ans --;
    }

    System.out.println(ans);
  }


}