Book 动态规划

虽然之前学过一点点，但是还是不会------现在好好跟着白书1.4节学一下——————

（1）数字三角形

d(i,j) = max(d(i+1,j),d(i+1,j+1)) + a[i][j]

hdu 2084

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include <cmath>
 #include<stack>
 #include<vector>
 #include<map>
 #include<set>
 #include<queue>
 #include<algorithm>
 using namespace std;

 typedef long long LL;
 const int INF = (<<)-;
 const int mod=;
 const int maxn=;

 int d[][],a[][];

 int main(){
     int T;
     scanf("%d",&T);
     while(T--){
         int n;
         scanf("%d",&n);
         memset(d,,sizeof(d));
         for(int i = ;i<=n;i++)
             for(int j = ;j<=i;j++) scanf("%d",&a[i][j]);

         for(int i = n;i>=;i--){
             for(int j = ;j<=i;j++)
             d[i][j] = max(d[i+][j],d[i+][j+]) + a[i][j];
         }
         printf("%d\n",d[][]);
     }
     return ;
 }

（2）嵌套矩形

把图先建出来，然后d(i) = max(d(j) + 1)

nyoj 16

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include <cmath>
 #include<stack>
 #include<vector>
 #include<map>
 #include<set>
 #include<queue>
 #include<algorithm>
 using namespace std;

 typedef long long LL;
 const int INF = (<<)-;
 const int mod=;
 const int maxn=;

 int g[][];
 int d[];
 int n;

 struct node{
     int x,y;
 }a[maxn];

 int dp(int i){
     int& ans = d[i];
     if(ans > ) return ans;
     ans = ;
     for(int j = ;j <= n;j++)
     if(g[i][j]) ans = max(ans,dp(j) + );

     return ans;
 }

 int work(){
     int res = -;
     for(int i = ;i <= n;i++) res = max(res,dp(i));
     return res;
 }

 int main(){
     int T;
     scanf("%d",&T);
     while(T--){
         scanf("%d",&n);
         for(int i = ;i <= n;i++) scanf("%d %d",&a[i].x,&a[i].y);
         memset(g,,sizeof(g));
         memset(d,,sizeof(d));

         for(int i = ;i <= n;i++){
             for(int j = ;j <= n;j++){
                 if((a[i].x > a[j].x && a[i].y > a[j].y) || (a[i].x > a[j].y && a[i].y > a[j].x ))
                 g[i][j] = ;
             }
         }

         printf("%d\n",work());
     }
     return ;
 }