JavaAlgorithms/DynamicProgramming/LongestIncreasingSubsequence.java

60 lines
1.4 KiB
Java
Raw Normal View History

package DynamicProgramming;
2017-09-29 11:47:05 +08:00
import java.util.Scanner;
2020-10-24 18:23:28 +08:00
/** @author Afrizal Fikri (https://github.com/icalF) */
2017-09-29 11:47:05 +08:00
public class LongestIncreasingSubsequence {
2020-10-24 18:23:28 +08:00
public static void main(String[] args) {
2017-09-29 11:47:05 +08:00
2020-10-24 18:23:28 +08:00
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
2017-09-29 11:47:05 +08:00
2020-10-24 18:23:28 +08:00
int ar[] = new int[n];
for (int i = 0; i < n; i++) {
ar[i] = sc.nextInt();
2017-09-29 11:47:05 +08:00
}
2020-10-24 18:23:28 +08:00
System.out.println(LIS(ar));
sc.close();
}
2017-09-29 11:47:05 +08:00
2020-10-24 18:23:28 +08:00
private static int upperBound(int[] ar, int l, int r, int key) {
while (l < r - 1) {
int m = (l + r) >>> 1;
if (ar[m] >= key) r = m;
else l = m;
2017-09-29 11:47:05 +08:00
}
2020-10-24 18:23:28 +08:00
return r;
}
2020-10-24 18:23:28 +08:00
private static int LIS(int[] array) {
int N = array.length;
if (N == 0) return 0;
2020-10-24 18:23:28 +08:00
int[] tail = new int[N];
2020-10-24 18:23:28 +08:00
// always points empty slot in tail
int length = 1;
2017-09-29 11:47:05 +08:00
2020-10-24 18:23:28 +08:00
tail[0] = array[0];
for (int i = 1; i < N; i++) {
2017-09-29 11:47:05 +08:00
2020-10-24 18:23:28 +08:00
// new smallest value
if (array[i] < tail[0]) tail[0] = array[i];
2017-09-29 11:47:05 +08:00
2020-10-24 18:23:28 +08:00
// array[i] extends largest subsequence
else if (array[i] > tail[length - 1]) tail[length++] = array[i];
2020-10-24 18:23:28 +08:00
// array[i] will become end candidate of an existing subsequence or
// Throw away larger elements in all LIS, to make room for upcoming grater elements than
// array[i]
// (and also, array[i] would have already appeared in one of LIS, identify the location and
// replace it)
else tail[upperBound(tail, -1, length - 1, array[i])] = array[i];
2017-09-29 11:47:05 +08:00
}
2020-10-24 18:23:28 +08:00
return length;
}
}