3090880_ac_732ms_800k.cc

来自「北大大牛代码 1240道题的原代码 超级权威」· CC 代码 · 共 52 行

#include <stdio.h>

int main()
    {
        int i, j, k, n;
        int  len[50001];
        int left[50001];
        int right[50001] ;
        
        while(scanf("%d",&n)==1)
        {
            for(i = 0; i < n; i++)
            {
                scanf("%d",&len[i]);
            }
            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
                {
                    while(r>i&&left[r]>=i&&r-i>ans)
						r = left[r];
					r = r-i;
					if(r > ans)
						ans = r;
                }
            }
            printf("%d\n",ans);
        }
return 0;
    }