ACM-ICPC 2017 沈阳赛区现场赛 G. Infinite Fraction Path && HDU 6223（BFS）

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=6223

参考题解：https://blog.csdn.net/qq_40482495/article/details/78492841

注意优先队列自定义比较级的用法！！

 #include <bits/stdc++.h>
 using namespace std;
 #define ll long long
 #define ull unsigned long long
 #define mst(a,b) memset((a),(b),sizeof(a))
 #define mp(a,b) make_pair(a,b)
 #define pi acos(-1)
 #define pii pair<int,int>
 #define pb push_back
 const int INF = 0x3f3f3f3f;
 const double eps = 1e-;
 const int MAXN = 15e4 + ;
 const int MAXM = 2e6 + ;

 char s[MAXN];
 int a[MAXN], ans[MAXN], vis[MAXN], nex[MAXN];

 struct node {
     int pos,val,dep;
 };

 struct cmp {
     bool operator()(const node &x,const node &y) {
         if(x.dep != y.dep) return x.dep > y.dep;
         else if(x.val != y.val) return x.val < y.val;
         return x.pos < y.pos;
     }
 };

 int main() {
 #ifdef local
     freopen("data.txt", "r", stdin);
 #endif
     int cas = ;
     int t;
     scanf("%d",&t);
     while(t--) {
         int n;
         scanf("%d",&n);
         scanf("%s",s);
         int mx = ;
         for(int i = ; i < n; i++) {
             ans[i] = vis[i] = -;
             a[i] = s[i] - '';
             mx = max(mx, a[i]);
             nex[i] = (1ll * i * i + ) % n;
         }
         priority_queue<node, vector<node>, cmp >q;
         for(int i = ; i < n; i++)
             if(a[i] == mx) q.push({i,a[i],});
         while(!q.empty()) {
             node now = q.top();
             q.pop();
             int pos = now.pos, val = now.val, dep = now.dep;
             if(dep >= n) break;
             if(ans[dep] > val) continue;
             else if(ans[dep] == val && vis[pos] == dep) continue;
             ans[dep] = val, vis[pos] = dep;
             q.push({nex[pos],a[nex[pos]],dep + });
         }
         printf("Case #%d: ",cas++);
         for(int i = ; i < n; i++) printf("%d",ans[i]);
         printf("\n");
     }
     return ;
 }