Gym - 100637B Lunch 规律

题意：n个点，给定起点和终点，可以每次可以走一格或两格，走一格则需要一个代价，每个格子只能走一次，问从起点到终点并经过每一个点的最小代价

思路：这题我没看出什么道理，先打了个暴力，结果发现了个相当坑的规律，，然后就过了。

 #include <iostream>
 #include <cstdio>
 #include <fstream>
 #include <algorithm>
 #include <cmath>
 #include <deque>
 #include <vector>
 #include <queue>
 #include <string>
 #include <cstring>
 #include <map>
 #include <stack>
 #include <set>
 #define LL long long
 #define eps 1e-8
 #define INF 0x3f3f3f3f
 #define MAXN 200005
 using namespace std;
 int main()
 {
 #ifndef ONLINE_JUDGE
     freopen("in.txt", "r", stdin);
     freopen("out.txt", "w", stdout);
 #endif // OPEN_FILE
     int n, s, t, o;
     while(~scanf("%d%d%d", &n, &s, &t)){
         //printf("%d %d %d %d ", n, s, t, o);
         int ans;
         if(s == t){
             ans = ;
         }
         else{
             if(s > t){
                 swap(s, t);
             }
             if(t - s == ){
                 if(s !=  && t != n){
                     ans = -;
                 }
                 else{
                     ans = ;
                 }
             }
             else{
                 int tt = n -s + ;
                 int ss = n - t + ;
                 if(ss < s){
                     s = ss;
                     t = tt;
                 }
                 int p;
                 if(s == ){
                     p = t - s - ;
                     ans =  + p /  + (p % );
                 }
                 else{
                     p = t - s - ;
                     ans =  + p /   + (p % );
                 }
             }
         }
         if(s ==  && t == n && n %  == ){
             ans -= ;
         }
         printf("%d\n", ans);
     }
     /*while(~scanf("%d%d%d", &n, &s, &t)){
         memset(vis, 0, sizeof(vis));
         vis[s] = true;
         vis[t] = true;
         ans = INF;
         dfs(s, 0, 0);
         if(ans == INF){
             printf("%d %d %d -1\n", n, s, t);
             continue;
         }
         printf("%d %d %d %d\n", n, s, t, ans);
     }*/
 }

下面是暴力的

 #include <iostream>
 #include <cstdio>
 #include <fstream>
 #include <algorithm>
 #include <cmath>
 #include <deque>
 #include <vector>
 #include <queue>
 #include <string>
 #include <cstring>
 #include <map>
 #include <stack>
 #include <set>
 #define LL long long
 #define eps 1e-8
 #define INF 0x3f3f3f3f
 #define MAXN 200005
 int n, s, t;
 int ans;
 bool vis[MAXN];
 using namespace std;
 void dfs(int x, int cnt, int cost){
     if(cnt == n - ){
         if(abs(x - t) == ){
             ans = min(ans, cost + );
         }
         else if(abs(x - t) == ){
             ans = min(ans, cost);
         }
         else{
             return;
         }
     }
     int y;
     for(int i = ; i <= ; i++){
         int p = i ==  ?  : ;
         y = x + i;
         if(y >=  && y <= n && !vis[y]){
             vis[y] = true;
             dfs(y, cnt + , cost + p);
             vis[y] = false;
         }
         y = x - i;
         if(y >=  && y <= n && !vis[y]){
             vis[y] = true;
             dfs(y, cnt + , cost + p);
             vis[y] = false;
         }
     }
 }
 int main()
 {
 #ifndef ONLINE_JUDGE
     freopen("in.txt", "r", stdin);
     //freopen("out.txt", "w", stdout);
 #endif // OPEN_FILE

     while(~scanf("%d%d%d", &n, &s, &t)){
         memset(vis, , sizeof(vis));
         vis[s] = true;
         vis[t] = true;
         ans = INF;
         dfs(s, , );
         if(ans == INF){
             printf("-1\n");
             return ;
         }
         printf("%d\n", ans);
     }
 }