[G2] 12738 가장 긴 증가하는 부분 수열 3

java/src/boj12738/Main.java

@@ -0,0 +1,61 @@
+package boj12738;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.ArrayList;
+import java.util.Arrays;
+
+public class Main {
+
+    private static final BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
+
+    public static void main(String[] args) {
+        int n = Integer.parseInt(readLine());
+        long[] data = Arrays.stream(readLine().split(" "))
+                .mapToLong(Long::parseLong)
+                .toArray();
+
+        ArrayList<Long> list = new ArrayList<>();
+        list.add(data[0]);
+
+        for (int i = 1; i < n; i++) {
+            long target = data[i];
+            if (list.get(list.size() - 1) < target) {
+                list.add(target);
+            } else {
+                int index = indexOf(list, target);
+                list.set(index, target);
+            }
+        }
+
+        System.out.println(list.size());
+    }
+
+    private static int indexOf(ArrayList<Long> list, long target) {
+        int start = 0;
+        int end = list.size() - 1;
+
+        while (start <= end) {
+            int middle = (start + end) / 2;
+            long compareTarget = list.get(middle);
+            if (compareTarget < target) {
+                start = middle + 1;
+            } else if (compareTarget == target) {
+                return middle;
+            } else {
+                end = middle - 1;
+            }
+        }
+
+        return start;
+    }
+
+    private static String readLine() {
+        try {
+            return reader.readLine();
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}