SPOJ 15 - The Shortest Path[SHPATH]
题目就是要求最短路,我们根据数据规模采用Dijkstra+Heap的算法。这里C++如果使用STL中的堆是没有办法过的。
#include <cstdio> #include <climits> #include <cstring> #include <string> #include <vector> #include <algorithm> using namespace std; const int MAXN = 10000+5; typedef pair<int,int> pii; typedef pair<string,int> psi; typedef vector<pii>::iterator iter; vector<pii> road[MAXN]; vector<psi> city; int n,dis[MAXN],size; int heap[MAXN],hash[MAXN]; inline void trylo(int u) { int tmp = heap[u],i = u; while (i*2+1<size) { int j = i*2+1; if (dis[heap[j+1]]<dis[heap[j]]) j++; if (dis[heap[j]]<dis[tmp]) { heap[i] = heap[j]; hash[heap[i]] = i; i = j; } else break; } heap[i] = tmp; hash[heap[i]] = i; } inline void tryhi(int u) { int tmp = heap[u],i = u; while (i>0) { int j = (i-1)/2; if (dis[tmp]<dis[heap[j]]) { heap[i] = heap[j]; hash[heap[i]] = i; i = j; } else break; } heap[i] = tmp; hash[heap[i]] = i; } inline void push(int u) { heap[size] = u; hash[u] = size++; tryhi(size-1); } inline int htop() { int ret = heap[0]; hash[heap[0]] = -1; heap[0] = heap[size-1]; hash[heap[0]] = 0; size--; trylo(0); return ret; } int dijkstra(int x,int y) { memset(dis,127,sizeof(dis)); dis[x] = 0; size = 0; memset(hash,-1,sizeof(hash)); push(x); while (size) { int u = htop(); for (iter i = road[u].begin(); i!=road[u].end(); ++i) { int v = i->second; if (dis[v]>dis[u]+i->first) { dis[v] = dis[u]+i->first; if (hash[v]==-1) push(v); else tryhi(hash[v]); } } } return dis[y]; } int main() { int ncase; scanf("%d",&ncase); while (ncase--) { scanf("%d",&n); city.clear(); for (int i = 0,m; i<n; i++) { char _name[16]; scanf("%s%d",_name,&m); city.push_back(psi(string(_name),i)); road[i].clear(); for (int j = 0,t,c; j<m; j++) { scanf("%d%d",&t,&c); t--; road[i].push_back(pii(c,t)); } } sort(city.begin(),city.end()); int query; scanf("%d",&query); while (query--) { char _na[16],_nb[16]; scanf("%s%s",_na,_nb); int ia = lower_bound(city.begin(),city.end(),psi(string(_na),0))->second; int ib = lower_bound(city.begin(),city.end(),psi(string(_nb),0))->second; printf("%d\n",dijkstra(ia,ib)); } } return 0; }
Your program in C++ from 2010-03-20 04:16:58 ran for 2.66 seconds and used 7020 KB of memory.
本作品遵循“署名-非商业性使用-相同方式共享 3.0 Unported”协议,转载请注明来自richard-desktop。