POJ 1821 Fence

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <algorithm>
 5 using namespace std;
 6 const int maxn = 20100;
 7 struct Worker{
 8     int L,S,P;
 9     bool operator<(const Worker &rhs) const{
10         return S < rhs.S;
11     }
12 }a[maxn];
13 int n,m,L[maxn],R[maxn],dp[110][maxn],q[maxn];
14 
15 int main(){
16     while(~scanf("%d%d",&n,&m)){
17         for(int i = 1; i <= m; ++i)
18             scanf("%d%d%d",&a[i].L,&a[i].P,&a[i].S);
19         sort(a + 1, a + m + 1);
20         for(int i = 1; i <= m; ++i){
21             L[i] = max(0,a[i].S - a[i].L);
22             R[i] = min(n,a[i].S + a[i].L - 1);
23         }
24         for(int i = 1; i <= m; ++i){
25             for(int j = 0; j <= R[i]; ++j)
26                 dp[i][j] = dp[i-1][j];
27             int hd = 0,tl = 0;
28             for(int j = L[i]; j < a[i].S; ++j){
29                 while(hd < tl && dp[i-1][j] - j*a[i].P >= dp[i-1][q[tl-1]] - q[tl-1]*a[i].P) --tl;
30                 q[tl++] = j;
31             }
32             for(int j = a[i].S; j <= R[i]; ++j){
33                 while(hd < tl && j - q[hd] > a[i].L) ++hd;
34                 dp[i][j] = max(dp[i-1][j],dp[i][j-1]);
35                 dp[i][j] = max(dp[i][j],dp[i-1][q[hd]] + (j - q[hd])*a[i].P);
36             }
37             for(int j = R[i] + 1; j <= n; ++j)
38                 dp[i][j] = max(dp[i-1][j],dp[i][j-1]);
39         }
40         int ret = 0;
41         for(int i = 1; i <= n; ++i)
42             ret = max(ret,dp[m][i]);
43         printf("%d\n",ret);
44     }
45     return 0;
46 }