hrbeu 哈工程 Who Is In Front of Me

//DP入门题状态转移方程很容易想到
//关键是构建pre数组，多少有点像KMP里面构建的next数组


#include <stdio.h>
#include <string.h>
#define MAX 50100
int a[MAX],pre[MAX],dp[MAX];
int n;
int main()
{
        int i,j,T,max;
        scanf("%d",&T);
        while(T--)
        {
                scanf("%d",&n);
                pre[1]=0;  dp[1]=0;
                scanf("%d",&a[1]);
                max=0;
                for(i=2; i<=n; i++)
                {
                        scanf("%d",&a[i]);
                        if(a[i]<a[i-1]) 
                        {
                                pre[i]=i-1;
                                dp[i]=dp[i-1]+1;
                        }
                        else
                        {
                                for(j=pre[i-1]; j!=0 && a[i]>=a[j] ; j=pre[j]) ;
                                pre[i]=j;
                                if(!pre[i])  dp[i]=0;
                                else         dp[i]=dp[pre[i]]+1;
                        }
                        max=dp[i]>max?dp[i]:max;
                }

//              for(i=1; i<=n; i++) printf("%d ",pre[i]); printf("\n");
//              for(i=1; i<=n; i++) printf("%d ",dp[i]);  printf("\n");
                printf("%d\n",max);
        }
        return 0;
}