public class SequentialSearch {
     public static void main(String[] args) {
         int n = Integer.parseInt(args[0]);
         int[] a = {50, 30, 40, 10, 20};
 
         int i = search(a, n);
         if (i >= 0) {
             System.out.println(n + " was found.(index = " + i + ")");
         } else {
             System.out.println(n + " was not found.");
         }
     }
     static int search(int[] a, int n) {
         for (int i = 0; i < a.length; i++) {
             if (a[i] == n) {
                 return i;
             }
         }
         return -1;
     }
 }

□ 実行結果

$java SequentialSearch 50
50 was found.(index = 0)

$java SequentialSearch 51
51 was not found.

 public class BinarySearch {
     public static void main(String[] args) {
         int n = Integer.parseInt(args[0]);
         int[] a = {10, 20, 30, 40, 50};
 
         int i = search(a, n);
         if (i >= 0) {
             System.out.println(n + " was found.(index = " + i + ")");
         } else {
             System.out.println(n + " was not found.");
         }
     }
     static int search(int[] a, int n) {
         int l = 0;
         int h = a.length - 1;
         int m;
         while (l <= h) {
             m = (l + h) / 2;
             if (a[m] < n) {
                 l = m + 1;
             } else if (a[m] > n) {
                 h = m - 1;
             } else {
                 return m;
             }
         }
         return -1;
     }
 }

□ 実行結果

$java BinarySearch 50
50 was found.(index = 4)

$java BinarySearch 51
51 was not found.

 public class Rank01 {
     public static void main(String[] args) {
         int[] a = {5, 3, 6, 5, 8, 6, 9, 1, 3, 3};
         int[] rank = new int[a.length];
 
         for (int i = 0; i < a.length; i++) {
             rank[i] = 1;
             for (int j = 0; j < a.length; j++) {
                 if (a[j] > a[i]) {
                     rank[i]++;
                 }
             }
         }
 
         for (int i = 0; i < a.length; i++) {
             System.out.println(a[i] + " - " + rank[i]);
         }
     }
 }

□ 実行結果

$java Rank01
5 - 5
3 - 7
6 - 3
5 - 5
8 - 2
6 - 3
9 - 1
1 - 10
3 - 7
3 - 7

 public class Count01 {
     public static void main(String[] args) {
         int[] a = {2, 2, 3, 5, 5, 5, 7, 8, 8};
 
         int prevValue = a[0];
         int count = 0;
         for (int i = 0; i < a.length; i++) {
             if (prevValue == a[i]) {
                 count++;
             } else {
                 System.out.println(prevValue + " : " + count);
                 count = 1;
                 prevValue = a[i];
             }
         }
         System.out.println(prevValue + " : " + count);
     }
 }

□ 実行結果

$java Count01
2 : 2
3 : 1
5 : 3
7 : 1
8 : 2

• 配列aに同じ数値になる要素はありません。
• 配列bに同じ数値になる要素はありません。
• 配列aとbで同じ要素があったときは、片方だけを配列cに追加します。
• 配列a,b,cの最後の要素はint型の最大値です。

 public class Matching01 {
     public static void main(String[] args) {
         int[] a = {10, 20, 30, 40, 50, Integer.MAX_VALUE};
         int[] b = {15, 20, 30, 35, 50, 60, Integer.MAX_VALUE};
 
         System.out.println(ArrayUtil.toString(match(a, b)));
     }
 
     static int[] match(int[] a, int[] b) {
         int[] c = new int[a.length + b.length];
         int i = 0, j = 0, k = 0;
         while (a[i] < Integer.MAX_VALUE || b[j] < Integer.MAX_VALUE) {
             if (a[i] < b[j]) {
                 c[k++] = a[i++];
             } else if (a[i] == b[j]) {
                 c[k++] = a[i++];
                 j++;
             } else {
                 c[k++] = b[j++];
             }
         }
         c[k] = Integer.MAX_VALUE;
         return c;
     }
 }

□ 実行結果

$java Matching01
[10, 15, 20, 30, 35, 40, 50, 60, 2147483647, 0, 0, 0, 0]

 public class Sort01 {
     public static void main(String[] args) {
         int n = args.length;
         int[] a = new int[n];
         for (int i = 0; i < n; i++) {
             a[i] = Integer.parseInt(args[i]);
         }
 
         for (int i = 0; i < n - 1; i++) {
             for (int j = i + 1; j < n; j++) {
                 if (a[i] > a[j]) {
                     int t = a[i];
                     a[i] = a[j];
                     a[j] = t;
                 }
             }
         }
         System.out.println(ArrayUtil.toString(a));
     }
 }

□ 実行結果

$java Sort01 6 3 5 1
[1, 3, 5, 6]