3090808_wa.java

北大大牛代码 1240道题的原代码 超级权威

import java.util.*;

public class Main
{
    public static void main(String[] args)
    {
        Scanner cin = new Scanner(System.in);
        int i, j, k, n;
        int min, max, mid;
        int [] len = new int [50001];
        int [] left = new int [50001];
        int [] right = new int [50001];
        
        while(cin.hasNext())
        {
            n = cin.nextInt();
            for(i = 0; i < n; i++)
            {
                len[i] = cin.nextInt();
            }
            left[0] = -1;
            for(j = 1; j < n; j++)
            {
                k = j-1;
                while(k!=-1&&len[k]<len[j])
                    k = left[k];
                left[j] = k;
            }
            right[n-1] = n;
            for(j = n-2; j >= 0; j--)
            {
                k = j+1;
                while(k!=n&&len[k]>len[j])
                    k = right[k];
                right[j] = k;
            }
            int ans = -1;
            for(i = 0; i < n-1; i++)
            {
                int r;
                r = right[i]-1;
                if(r==i||r-i<=ans)
                    continue;
                else
                {
                    boolean fail = false;
                    min = i+1;max = r;
                    while(min < max)
                    {
                        if(max - i <= ans)
                        {
                            fail = true;
                            break;
                        }
                        mid = (max+min)>>1;
                        if(left[mid]<i)
                        {
                            min = mid+(min==mid?1:0);
                        }
                        else
                        {
                            max = mid;
                        }
                    }
                    if(fail)
                        continue;
                    if(left[min]>=i)
                        min--;
                    min = min-i;
                    if(min > ans)
                        ans = min;
                }
            }
            System.out.println(ans);
        }
    }

}