本文主要是介绍1018. Public Bike Management 解析，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
单用Dijstra算法比较难维护。用Dijstra+DFS能简化不少。
看到有小伙伴例7有问题，可以看下是不是Dijstra的算法在计算路径的时候出问题没。我的就是下标u和i弄混了。查了好久。。。。。
#include <iostream>
#include <vector>
#include <string>
#include <climits>
#include <stack>using namespace std;struct Node {int length;int Num;
};struct Grap {int bIkeNum;vector <Node> link;
};void Dijkstra(Grap * g, int * dis ,vector<int> * pre ,int N,bool * isvisit ) {dis[0] = 0;for (int i = 0; i < N; i++) {int u = -1, Min = INT_MAX;for (int j = 0; j < N; j++) { //找Dis最小值if (!isvisit[j] && dis[j] < Min) {u = j;Min = dis[j];}}if (u == -1) return;isvisit[u] = true; for (int j = 0; j < g[u].link.size(); j++) {int v = g[u].link[j].Num;if (!isvisit[v]) {if (dis[u] + g[u].link[j].length < dis[v]) {//u是中间结点pre[v].clear();pre[v].push_back(u);dis[v] = dis[u] + g[u].link[j].length;}else if (dis[u] + g[i].link[j].length == dis[v]) {pre[v].push_back(u);}}}}
}void DFS(vector <int> * pre, vector <int> & patch, vector <int> & tempatch, Grap * g, int & BikeNeed, int & BikeReturn, int v, int Cmax) {//cout << " v = " << v << endl;int perfect = Cmax / 2;if (v == 0) {tempatch.push_back(v);int bn = 0, br = 0;//计算大小//cout << "size: " << tempatch.size() << endl;for (int i = tempatch.size() - 1; i >= 0; i--) {int b = g[tempatch[i]].bIkeNum;if (b > perfect) {//大于perfect需要带走br += b - perfect;}else if (b < perfect){ //补齐br -= (perfect - b);// cout << "br : " << br << endl;if (br < 0) {//不够补齐 要从中心调bn += (-br);br = 0;}}}//判断if (bn < BikeNeed) {BikeNeed = bn;BikeReturn = br;patch = tempatch;}else if (bn == BikeNeed && br < BikeReturn) {BikeNeed = bn;BikeReturn = br;patch = tempatch;}tempatch.pop_back();return;}tempatch.push_back(v);for (int i = 0; i < pre[v].size(); i++) {DFS(pre, patch, tempatch, g, BikeNeed, BikeReturn, pre[v][i], Cmax);}tempatch.pop_back();}int main() {int Cmax, N, SP, M;//Cmax最大容量，N站总数，SP问题站编号，M道路总数cin >> Cmax >> N >> SP >> M;Grap * g = new Grap[N + 1];stack <int> s;for (int i = 1; i <= N; i++) {cin >> g[i].bIkeNum;}g[0].bIkeNum = Cmax / 2;Node tempNode;int tempHead, tempTail;for (int i = 0; i < M; i++) {cin >> tempHead >> tempTail >> tempNode.length;tempNode.Num = tempTail;g[tempHead].link.push_back(tempNode);//cout << tempHead << " " << tempNode.Num << " " << tempNode.length << endl;tempNode.Num = tempHead;g[tempTail].link.push_back(tempNode);//cout << tempTail << " " << tempNode.Num << " " << tempNode.length << endl;}// int MinLegnth = INT_MAX;bool * isVisit = new bool[N + 1];int * dis = new int[N + 1];vector <int> * pre = new vector<int>[N + 1];for (int i = 0; i <= N; i++) {dis[i] = INT_MAX;isVisit[i] = false;}Dijkstra(g, dis, pre, N + 1, isVisit);int BikeNeed = INT_MAX, BikeReturn = INT_MAX;vector <int> patch, tempatch;DFS(pre, patch, tempatch, g, BikeNeed, BikeReturn, SP, Cmax);cout << BikeNeed << " ";for (int i = patch.size() - 1; i > 0; i--) {cout << patch[i] << "->";}cout << patch[0] << " ";cout << BikeReturn << endl;system("pause");return 0;
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