洛谷P3957 跳房子

普及组的题.....填坑来了。

当年的我一眼二分+DP，现在都佩服起自己来了......

然后我们就写个二分，在check里面写单调队列优化DP即可。

然后就A了......

 #include <cstdio>
 #include <cstring>
 #include <algorithm>

 typedef long long LL;
 const int N = ;
 const LL INF = (1ll << );

 int n, x[N];
 LL v[N], k;

 int p[N], head, top;
 LL f[N];

 inline bool check(int L, int R) {
     memset(f, 0xcf, sizeof(f));
     LL ans = -INF;
     f[] = ;
     head = ;
     top = ;
     int pos_in = ;
     for(int i = ; i <= n; i++) {
         while(x[i] - x[pos_in] >= L) {
             p[++top] = pos_in;
             while(head < top && f[p[top]] > f[p[top - ]]) {
                 p[top - ] = p[top];
                 top--;
             }
             pos_in++;
         }
         while(head <= top && x[i] - x[p[head]] > R) {
             head++;
         }

         if(head <= top) {
             f[i] = f[p[head]] + v[i];
         }

         ans = std::max(ans, f[i]);
     }
     return ans >= k;
 }

 int main() {
     int d;
     LL sum = ;
     scanf("%d%d%lld", &n, &d, &k);
     for(int i = ; i <= n; i++) {
         scanf("%d%lld", &x[i], &v[i]);
         sum += std::max(v[i], 0ll);
     }
     if(sum < k) {
         printf("-1");
         return ;
     }

     int l = , r = std::max(x[n] - d, d), mid;
     while(l < r) {
         mid = (l + r) >> ;
         if(check(std::max(, d - mid), d + mid)) {
             r = mid;
         }
         else {
             l = mid + ;
         }
     }

     printf("%d", r);
     return ;
 }

AC代码