【PAT Advanced Level】1018. Public Bike Management (30)

这题还是比较有难度的。题目中要纪录的东西比较多，比较繁琐。

这题我考虑先用Dijkstra算法计算单源最短路径，在计算过程中纪录每个点的最短路径的前序（如果最短路径有多条，每个前序都需要纪录），然后再递归深搜出具有最少携带自行车数量的路径。

这题还有几个点没过，先放着吧，感觉整体思路没什么问题。

#include <iostream>#include <memory.h>#include <fstream>#include <stack>#include <vector>#include <algorithm>using namespace std;const int maxInt = 0x7fffffff;const int maxStation = 501;int road[501][501];int bikeCount[501];bool visited[501];int capacity, stationNum, proStation, roadsNum;struct node{int index;int minDistance;vector<int> preNode;node(int i, int minDistance) : index(i), minDistance(minDistance) {}};vector<node> q;vector<node> s;int minBike = maxInt;vector<int> result;bool cmp(const node &n1, const node &n2){return n1.minDistance > n2.minDistance;}bool cmpbyIndex(const node &n1, const node &n2){return n1.index > n2.index;}void Dijkstra(){s.push_back(node(0, 0));for(int i = 1; i <= stationNum; i++)s.push_back(node(i, maxInt));while (!s.empty()){make_heap(s.begin(), s.end(), cmp);pop_heap(s.begin(), s.end(), cmp);node tmp = s.back();s.pop_back();for(int i = 0; i < s.size(); i++){if(road[tmp.index][s[i].index]){if(tmp.minDistance + road[tmp.index][s[i].index] < s[i].minDistance){s[i].minDistance = tmp.minDistance + road[tmp.index][s[i].index];s[i].preNode.clear();s[i].preNode.push_back(tmp.index);}else if(tmp.minDistance + road[tmp.index][s[i].index] == s[i].minDistance)s[i].preNode.push_back(tmp.index);}}q.push_back(tmp);}}int getPath(int index, int cur, vector<int> path){const int need = bikeCount[proStation] - capacity/2;sort(s.begin(), s.end(), cmpbyIndex);if(index == 0){if(abs(cur + need + 5) < abs(minBike + need + 5)){minBike = cur;result = path;}return 0;}for(int i = 0; i < q[index].preNode.size(); i++){path.push_back(q[index].preNode[i]);getPath(q[index].preNode[i], bikeCount[q[index].preNode[i]] - capacity/2 + cur, path);path.pop_back();}}int main(){fstream cin("a.txt");cin>>capacity>>stationNum>>proStation>>roadsNum;for(int i = 1; i <= stationNum; i++)cin>>bikeCount[i];for(int i = 0; i < roadsNum; i++){int row, colunm, tmp;cin>>row>>colunm>>tmp;road[row][colunm] = road[colunm][row] = tmp;}memset(visited, 0, sizeof(visited)/sizeof(bool));Dijkstra();getPath(proStation, 0, vector<int>());//system("pause");int tmp = bikeCount[proStation] + minBike;if(tmp < 0)cout<<abs(tmp)<<" ";else cout<<0<<" ";reverse(result.begin(), result.end());for (int i = 0; i < result.size(); i++){cout<<result[i]<<"->";}cout<<proStation<<" ";if(tmp > 0)cout<<tmp<<endl;else cout<<0<<endl;}