【HDOJ】2217 Visit

挺好的一道DP。

 /* 2217 */
 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <cstdlib>
 #include <algorithm>
 using namespace std;

 #define MAXN 2005
 #define MAXM 100005

 int lt[MAXN], rt[MAXN];
 int ldp[MAXM], rdp[MAXM];
 int ln, rn, zn;

 int main() {
     int n, t;
     int i, j, k, tmp;
     int ans;

     #ifndef ONLINE_JUDGE
         freopen("data.in", "r", stdin);
     #endif

     while (scanf("%d %d", &n, &t) != EOF) {
         ln = rn = ;
         zn = ;
         lt[] = ;
         rt[] = ;
         for (i=; i<n; ++i) {
             scanf("%d", &k);
             if (k > )
                 rt[rn++] = k;
             else if (k < )
                 lt[ln++] = -k;
             else
                 ++zn;
         }

         rt[] = ;
         lt[] = ;
         sort(rt, rt+rn);
         sort(lt, lt+ln);
         ldp[] = ;
         rdp[] = ;

         k = ;
         for (i=; i<ln; ++i) {
             for (j=lt[i-]; j<lt[i]; ++j)
                 ldp[j] = k;
             ++k;
             ldp[j] = k;
         }

         k = ;
         for (i=; i<rn; ++i) {
             for (j=rt[i-]; j<rt[i]; ++j)
                 rdp[j] = k;
             ++k;
             rdp[j] = k;
         }

         ans = -;
         // go left and back to right
         for (i=; i<=lt[ln-]; ++i) {
             if (t < i)
                 break;
             k = t-(i+i);
             if (k < )
                 k = ;
             if (k > rt[rn-])
                 k = rt[rn-];

             ans = max(ans, ldp[i]+rdp[k]);
         }
         // go right and back to left
         for (i=; i<=rt[rn-]; ++i) {
             if (t < i)
                 break;
             k = t-(i+i);
             if (k < )
                 k = ;
             if (k > lt[ln-])
                 k = lt[ln-];

             ans = max(ans, rdp[i]+ldp[k]);
         }
         // go zero point first
         ans += zn;

         printf("%d\n", ans);
     }

     return ;
 }