HDU 1224 Free DIY Tour

题意：给出每个城市interesting的值，和城市之间的飞行路线，求一条闭合路线（从原点出发又回到原点）

使得路线上的interesting的值之和最大

因为要输出路径，所以用pre数组来保存前驱

在输出路径的时候，我是把前驱一次放在route数组里面，然后再将整个数组反转过来

另外，看别人的题解里面还有一种递归的方法求路径，挺有新意，学习了

我的做法：

 //#define LOCAL
 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 using namespace std;

 const int maxn = ;
 bool flight[][];
 int city[];
 int dp[];
 int pre[];
 int route[];

 int main(void)
 {
     #ifdef LOCAL
         freopen("1224in.txt", "r", stdin);
     #endif

     int N, kase;
     scanf("%d", &N);
     for(kase = ; kase <= N; ++kase)
     {
         if(kase > )    printf("\n");

         int n;
         scanf("%d", &n);
         int i;
         for(i = ; i <= n; ++i)
             scanf("%d", &city[i]);
         city[n + ] = ;

         int m, from, to;
         memset(flight, , sizeof(flight));
         scanf("%d", &m);
         for(i = ; i <= m; ++i)
         {
             scanf("%d%d", &from, &to);
             flight[from][to] = true;
         }

         memset(dp, , sizeof(dp));
         memset(pre, , sizeof(pre));
         int j;
         for(i = ; i <= n + ; ++i)
             for(j = ; j < i; ++j)
                 if(flight[j][i]
                     && (dp[j] + city[i]) > dp[i])
                 {
                     dp[i] = dp[j] + city[i];
                     pre[i] = j;
                 }

         printf("CASE %d#\n", kase);
         printf("points : %d\n", dp[n + ]);
         int p = n + , len = ;
         while(pre[p] != )
         {
             route[len++] = pre[p];
             p = pre[p];
         }
         for(i = ; i < len / ; ++i)
         {
             int t = route[i];
             route[i] = route[len - i -];
             route[len - i -] = t;
         }

         printf("circuit : ");
         for(i = ; i < len; ++i)
             printf("%d->", route[i]);
         printf("1\n");
     }

     return ;
 }

代码君

别人递归回溯输出路径的做法：

 //#define LOCAL
 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <algorithm>
 using namespace std;

 const int maxn = ;
 bool flight[][];
 int city[];
 int dp[];
 int pre[];
 int route[];

 void putroute(int p)
 {
     if(p == )
         return;
     putroute(pre[p]);
     printf("%d->", p);
 }

 int main(void)
 {
     #ifdef LOCAL
         freopen("1224in.txt", "r", stdin);
     #endif

     int N, kase;
     scanf("%d", &N);
     for(kase = ; kase <= N; ++kase)
     {
         if(kase > )    printf("\n");

         int n;
         scanf("%d", &n);
         int i;
         for(i = ; i <= n; ++i)
             scanf("%d", &city[i]);
         city[n + ] = ;

         int m, from, to;
         memset(flight, , sizeof(flight));
         scanf("%d", &m);
         for(i = ; i <= m; ++i)
         {
             scanf("%d%d", &from, &to);
             flight[from][to] = true;
         }

         memset(dp, , sizeof(dp));
         memset(pre, , sizeof(pre));
         int j;
         for(i = ; i <= n + ; ++i)
             for(j = ; j < i; ++j)
                 if(flight[j][i]
                     && (dp[j] + city[i]) > dp[i])
                 {
                     dp[i] = dp[j] + city[i];
                     pre[i] = j;
                 }

         printf("CASE %d#\n", kase);
         printf("points : %d\n", dp[n + ]);

         printf("circuit : ");
         putroute(pre[n + ]);
         printf("1\n");
     }

     return ;
 }

代码君