【Codeforces 977F】Consecutive Subsequence

【链接】 我是链接,点我呀:)

【题意】

题意

【题解】

设f[i]表示i作为序列的最后一个数字,最长的连续序列的长度。
用f[i]和f[i-1]+1来转移即可

【代码】

import java.io.*;
import java.util.*;

public class Main {

    static InputReader in;
    static PrintWriter out;

    public static void main(String[] args) throws IOException{
        //InputStream ins = new FileInputStream("E:\\rush.txt");
        InputStream ins = System.in;
        in = new InputReader(ins);
        out = new PrintWriter(System.out);
        //code start from here
        new Task().solve(in, out);
        out.close();
    }

    static int N = (int)2e5;
    static class Task{

        int n;
        HashMap<Integer,Integer> dic = new HashMap<Integer,Integer>();
        int a[] = new int[N+10];
        ArrayList<Integer> v = new ArrayList<Integer>();

        public void solve(InputReader in,PrintWriter out) {
        	n = in.nextInt();
        	int len = 0,idx = -1;
        	for (int i = 1;i <= n;i++) {
        		a[i] = in.nextInt();
        		int x = a[i];
        		if (dic.containsKey(x)) {
        			int cur = dic.get(x);
        			int temp = 0;
        			if (dic.containsKey(x-1)) {
        				temp = dic.get(x-1);
        			}
        			cur = Math.max(cur, temp+1);
        			dic.put(x, cur);
        		}else {
        			int temp = 0;
        			if (dic.containsKey(x-1)) {
        				temp = dic.get(x-1);
        			}
        			dic.put(x, temp+1);
        		}
        		int temp0 = dic.get(x);
        		if (temp0>len) {
        			len = temp0;
        			idx = i;
        		}
        	}
        	out.println(len);
        	int now = a[idx];
        	for (int i = idx;i >= 1;i--) {
        		if (a[i]==now) {
        			v.add(i);
        			now--;
        		}
        	}
        	for (int i = (int)v.size()-1;i >= 0;i--) {
        		out.print(v.get(i)+" ");
        	}

        }
    }

    static class InputReader{
        public BufferedReader br;
        public StringTokenizer tokenizer;

        public InputReader(InputStream ins) {
            br = new BufferedReader(new InputStreamReader(ins));
            tokenizer = null;
        }

        public String next(){
            while (tokenizer==null || !tokenizer.hasMoreTokens()) {
                try {
                tokenizer = new StringTokenizer(br.readLine());
                }catch(IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }
    }
}