Codeforces 279CLadder

Posted 2021-02-14 awcxv

【链接】 我是链接,点我呀:)
【题意】

题意

【题解】

设pre[i]表示i往前一直递增能递增多远
设aft[i]表示i往后一直递增能递增多远
如果aft[l]+pre[r]>=(r-l+1)那么就ok否则no

【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 = 50000;
    static class Task{
        
        int n,m;
        
        public void solve(InputReader in,PrintWriter out) {
            n = in.nextInt();m = in.nextInt();
            int a[] = new int[n+5];
            int aft[] = new int[n+5],pre[] = new int[n+5];
            for (int i = 1;i <= n;i++) a[i] = in.nextInt();
            for (int i = n;i >= 1;i--) {
                if (i+1<=n && a[i]<=a[i+1]) 
                    aft[i] = aft[i+1]+1;
                else
                    aft[i] = 1;
            }
            
            for (int i = 1;i <= n;i++) {
                if (i-1>=1 && a[i-1]>=a[i])
                    pre[i] = pre[i-1]+1;
                else
                    pre[i] = 1;
            }
            for (int i = 1;i <= m;i++) {
                int x,y;
                x = in.nextInt();y = in.nextInt();
                if (aft[x]+pre[y]>=(y-x+1)) {
                    System.out.println("Yes");
                }else {
                    System.out.println("No");
                }
            }
        }
    }

    

    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());
        }
    }
}