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プログラミングの勉強を始めた、情報学専攻の大学院生です。モチベーション維持のため、ブログに勉強したことを書いていきます。→就職。IT全然関係ない仕事をしています

AtCoder Beginner Contest 101 やりました

久々にAtCoderやりました。
abc101.contest.atcoder.jp

途中から参戦して、3問目まで解けました。4問目は解けず・・・4問目解けた人は、Beginnerの方にはほとんどいませんでした。数学的な問題で、取り組みがいがありました。
1〜3問目までの解答と、4問目も思考の経過を書きます。全部Java。いつもの長ったらしいテンプレ部分も書いてます。ご了承下さい。

1問目

import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.LinkedList;
import java.util.PriorityQueue;
 
 
 
public class Main {
  public static void main(String[] args) {
    InputReader sc = new InputReader(System.in);
 
    String n = sc.nextStr();
    int  ans = 0;
    for(int i = 0; i < n.length(); i++){
      if(n.charAt(i) == '+'){
        ans++;
      }else{
        ans--;
      }
    }
    System.out.println(ans);
 
  }
 
 //ここからテンプレ
  static class InputReader {
      private InputStream stream;
      private byte[] buf = new byte[1024];
      private int curChar;
      private int numChars;
      private SpaceCharFilter filter;
 
      public InputReader(InputStream stream) {
          this.stream = stream;
      }
 
      public int next() {
          if (numChars == -1)
              throw new InputMismatchException();
          if (curChar >= numChars) {
              curChar = 0;
              try {
                  numChars = stream.read(buf);
              } catch (IOException e) {
                  throw new InputMismatchException();
              }
              if (numChars <= 0)
                  return -1;
          }
          return buf[curChar++];
      }
 
      public String nextStr() {
        int c = next();
        while(isSpaceChar(c)){c = next();}
        StringBuffer str = new StringBuffer();
        do{
          str.append((char)c);
          c = next();
        }while(!isSpaceChar(c));
        return str.toString();
      }
 
      public char nextChar() {
        int c = next();
        while(isSpaceChar(c)){c = next();}
        char ret;
        do{
          ret = (char)c;
          c = next();
        }while(!isSpaceChar(c));
        return ret;
      }
 
      public int nextInt() {
          int c = next();
          while (isSpaceChar(c))
              c = next();
          int sgn = 1;
          if (c == '-') {
              sgn = -1;
              c = next();
          }
          int res = 0;
          do {
              if (c < '0' || c > '9')
                  throw new InputMismatchException();
              res *= 10;
              res += c - '0';
              c = next();
          } while (!isSpaceChar(c));
          return res * sgn;
      }
 
      public boolean isSpaceChar(int c) {
          if (filter != null)
              return filter.isSpaceChar(c);
          return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
      }
 
      public interface SpaceCharFilter {
          public boolean isSpaceChar(int ch);
      }
  }
}

2問目

import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.LinkedList;
import java.util.PriorityQueue;
 
 
 
public class Main {
  public static void main(String[] args) {
    InputReader sc = new InputReader(System.in);
 
    int n = sc.nextInt();
    int m = n;
    int s = 0;
    while(m > 0){
      s += m % 10;
      m /= 10;
    }
 
    if(n % s == 0){
      System.out.println("Yes");
    }else{
      System.out.println("No");
    }
  }
 
 //ここからテンプレ
  static class InputReader {
      private InputStream stream;
      private byte[] buf = new byte[1024];
      private int curChar;
      private int numChars;
      private SpaceCharFilter filter;
 
      public InputReader(InputStream stream) {
          this.stream = stream;
      }
 
      public int next() {
          if (numChars == -1)
              throw new InputMismatchException();
          if (curChar >= numChars) {
              curChar = 0;
              try {
                  numChars = stream.read(buf);
              } catch (IOException e) {
                  throw new InputMismatchException();
              }
              if (numChars <= 0)
                  return -1;
          }
          return buf[curChar++];
      }
 
      public String nextStr() {
        int c = next();
        while(isSpaceChar(c)){c = next();}
        StringBuffer str = new StringBuffer();
        do{
          str.append((char)c);
          c = next();
        }while(!isSpaceChar(c));
        return str.toString();
      }
 
      public char nextChar() {
        int c = next();
        while(isSpaceChar(c)){c = next();}
        char ret;
        do{
          ret = (char)c;
          c = next();
        }while(!isSpaceChar(c));
        return ret;
      }
 
      public int nextInt() {
          int c = next();
          while (isSpaceChar(c))
              c = next();
          int sgn = 1;
          if (c == '-') {
              sgn = -1;
              c = next();
          }
          int res = 0;
          do {
              if (c < '0' || c > '9')
                  throw new InputMismatchException();
              res *= 10;
              res += c - '0';
              c = next();
          } while (!isSpaceChar(c));
          return res * sgn;
      }
 
      public boolean isSpaceChar(int c) {
          if (filter != null)
              return filter.isSpaceChar(c);
          return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
      }
 
      public interface SpaceCharFilter {
          public boolean isSpaceChar(int ch);
      }
  }
}

3問目

最期の状態を考えてみると、結局全部1になるわけですね。
コーナーケースとして、「1がはじっこにあるもの」と、下記のようなケースに注意です。

7 3
2 3 6 1 5 4 7

※この場合、

2 3 6 1 5 4 7
2 3 1 1 1 4 7
1 1 1 1 1 4 7
1 1 1 1 1 1 1

と3回でできます。

import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.LinkedList;
import java.util.PriorityQueue;
 
 
 
public class Main {
  public static void main(String[] args) {
    InputReader sc = new InputReader(System.in);
 
    int n = sc.nextInt();
    int k = sc.nextInt();
 
    int[] nums = new int[n];
    int oneind = 0;
    for(int i = 0; i < n; i++){
      nums[i] = sc.nextInt();
      if(nums[i] == 1){
        oneind = i;
      }
    }
    int ans = 0;
    int yoyuu1 = 0;
    int yoyuu2 = 0;
 
    for(int i = 0; i < oneind; i += k - 1){
      ans++;
      yoyuu1 = i + k - 1;
    }
    for(int i = n - 1; i > oneind; i -= k - 1){
      ans++;
      yoyuu2 = i - k + 1;
    }
 
    if(yoyuu1 - yoyuu2 >= k - 1){
      ans--;
    }
    if(oneind == n - 1){
      ans++;
    }
    System.out.println(ans);
 
  }
 
 //ここからテンプレ
  static class InputReader {
      private InputStream stream;
      private byte[] buf = new byte[1024];
      private int curChar;
      private int numChars;
      private SpaceCharFilter filter;
 
      public InputReader(InputStream stream) {
          this.stream = stream;
      }
 
      public int next() {
          if (numChars == -1)
              throw new InputMismatchException();
          if (curChar >= numChars) {
              curChar = 0;
              try {
                  numChars = stream.read(buf);
              } catch (IOException e) {
                  throw new InputMismatchException();
              }
              if (numChars <= 0)
                  return -1;
          }
          return buf[curChar++];
      }
 
      public String nextStr() {
        int c = next();
        while(isSpaceChar(c)){c = next();}
        StringBuffer str = new StringBuffer();
        do{
          str.append((char)c);
          c = next();
        }while(!isSpaceChar(c));
        return str.toString();
      }
 
      public char nextChar() {
        int c = next();
        while(isSpaceChar(c)){c = next();}
        char ret;
        do{
          ret = (char)c;
          c = next();
        }while(!isSpaceChar(c));
        return ret;
      }
 
      public int nextInt() {
          int c = next();
          while (isSpaceChar(c))
              c = next();
          int sgn = 1;
          if (c == '-') {
              sgn = -1;
              c = next();
          }
          int res = 0;
          do {
              if (c < '0' || c > '9')
                  throw new InputMismatchException();
              res *= 10;
              res += c - '0';
              c = next();
          } while (!isSpaceChar(c));
          return res * sgn;
      }
 
      public boolean isSpaceChar(int c) {
          if (filter != null)
              return filter.isSpaceChar(c);
          return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
      }
 
      public interface SpaceCharFilter {
          public boolean isSpaceChar(int ch);
      }
  }
}

コーナーケース処理が一部ちゃんとできておらず、強引な書き方になりました。




4問目の途中経過(解けず・・・)

とりあえず、下記のようなコードを書いて、ideoneで試しました。
単純に全部試していくコードです。

import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.LinkedList;
import java.util.PriorityQueue;
 
 
 
public class Main {
  public static void main(String[] args) {
    InputReader sc = new InputReader(System.in);
 
    int n = sc.nextInt();

    int count = 0;
    double[] nums = new double[n + 1];
    nums[0] = 0.0;
    for(int i = 1; i < n + 1; i++){
      int ketawa = 0;
      int j = i;
      while(j > 0){
        ketawa += j % 10;
        j /= 10;
      }
      nums[i] = (double)i / (double)ketawa;
    }

    for(int i = 1; i < n; i++){
      boolean check = true;
      for(int j = i + 1; j < n; j++){
        if(nums[i] > nums[j]){
          check = false;
        }
      }
      if(check){
        System.out.println(i);
      }
    }
 
  }
 
 //ここからテンプレ
  static class InputReader {
      private InputStream stream;
      private byte[] buf = new byte[1024];
      private int curChar;
      private int numChars;
      private SpaceCharFilter filter;
 
      public InputReader(InputStream stream) {
          this.stream = stream;
      }
 
      public int next() {
          if (numChars == -1)
              throw new InputMismatchException();
          if (curChar >= numChars) {
              curChar = 0;
              try {
                  numChars = stream.read(buf);
              } catch (IOException e) {
                  throw new InputMismatchException();
              }
              if (numChars <= 0)
                  return -1;
          }
          return buf[curChar++];
      }
 
      public String nextStr() {
        int c = next();
        while(isSpaceChar(c)){c = next();}
        StringBuffer str = new StringBuffer();
        do{
          str.append((char)c);
          c = next();
        }while(!isSpaceChar(c));
        return str.toString();
      }
 
      public char nextChar() {
        int c = next();
        while(isSpaceChar(c)){c = next();}
        char ret;
        do{
          ret = (char)c;
          c = next();
        }while(!isSpaceChar(c));
        return ret;
      }
 
      public int nextInt() {
          int c = next();
          while (isSpaceChar(c))
              c = next();
          int sgn = 1;
          if (c == '-') {
              sgn = -1;
              c = next();
          }
          int res = 0;
          do {
              if (c < '0' || c > '9')
                  throw new InputMismatchException();
              res *= 10;
              res += c - '0';
              c = next();
          } while (!isSpaceChar(c));
          return res * sgn;
      }
 
      public boolean isSpaceChar(int c) {
          if (filter != null)
              return filter.isSpaceChar(c);
          return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
      }
 
      public interface SpaceCharFilter {
          public boolean isSpaceChar(int ch);
      }
  }
}


入力を1000000にしたら、こんな感じででてきました。

1
2
3
4
5
6
7
8
9
19
29
39
49
59
69
79
89
99
199
299
399
499
599
699
799
899
999
1099
1199
1299
1399
1499
1599
1699
1799
1899
1999
2999
3999
4999
5999
6999
7999
8999
9999
10999
11999
12999
13999
14999
15999
16999
17999
18999
19999
20999
21999
22999
23999
24999
25999
26999
27999
28999
29999
39999
49999
59999
69999
79999
89999
99999
109999
119999
129999
139999
149999
159999
169999
179999
189999
199999
209999
219999
229999
239999
249999
259999
269999
279999
289999
299999
309999
319999
329999
339999
349999
359999
369999
379999
389999
399999
499999
599999
699999
799999
899999
999999

とここでギブアップ。規則性を見つけられそうで見つけられず・・・
残念でした。

でも、久々にガッツリ目の問題に長く取り組めて楽しかったです。
それでは、CodingGameに戻ります。