HDU 3507 斜率优化 DP Print Article

在kuangbin巨巨博客上学的。

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

 using namespace std;

 const int maxn =  + ;
 int d[maxn], Q[maxn], sum[maxn];

 int head, tail;
 int n, M;

 int inline dx(int i, int j)
 {
     return sum[j] - sum[i];
 }

 int inline dy(int i, int j)
 {
     return d[j] + (sum[j]*sum[j]) - d[i] - (sum[i]*sum[i]);
 }

 int inline DP(int i, int j)
 {
     return d[i] + (sum[j]-sum[i])*(sum[j]-sum[i]) + M;
 }

 int main()
 {
     while(scanf("%d%d", &n, &M) ==  && n)
     {
         for(int i = ; i <= n; i++) scanf("%d", sum + i);
         for(int i = ; i <= n; i++) sum[i] += sum[i - ];

         head = tail = ;
         Q[tail++] = ;
         for(int i = ; i <= n; i++)
         {
             while(head +  < tail && dy(Q[head], Q[head + ]) <=  * sum[i] * dx(Q[head], Q[head + ])) head++;
             d[i] = DP(Q[head], i);
             while(head +  < tail && dy(Q[tail-], i) * dx(Q[tail-], Q[tail-]) <= dy(Q[tail-], Q[tail-]) * dx(Q[tail-], i)) tail--;
             Q[tail++] = i;
         }

         printf("%d\n", d[n]);
     }

     return ;
 }

代码君