1030. Travel Plan 解析

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直接Dijstra感觉简单点，这个第二标尺比较容易想明白。Dijstra+DFS感觉反而麻烦了一点两个都写了下练练手。

#include <iostream>#include <string>#include <vector>#include <algorithm>#include <climits>#include <stack>#define MAX 510using namespace std;struct Node {int v;int dis;int cost;};vector <Node> g[MAX];vector <bool> isVis;vector <int> pre[MAX];vector <int> dis;vector <int> cost;int P[MAX];int C[MAX];int N, M, S, D;void dijstra(int st) { //st 起点dis[st] = 0;C[st] = 0;for (int i = 0; i < N; i++) {int min = INT_MAX, u = -1;for (int j = 0;j < N; j++) { //找最小距离if (!isVis[j] && min > dis[j]) {min = dis[j];u = j;}}if (u == -1) return;//没有最小值isVis[u] = true;for (int j = 0; j < g[u].size(); j++) {int v = g[u][j].v;if (!isVis[v]) {if (dis[v] > dis[u] + g[u][j].dis) {dis[v] = dis[u] + g[u][j].dis;pre[v].clear();pre[v].push_back(u);//法二P[v] = u;C[v] = C[u] + g[u][j].cost;}else if (dis[v] == dis[u] + g[u][j].dis) {pre[v].push_back(u);//法二if (C[v] > C[u] + g[u][j].cost) {P[v] = u;C[v] = C[u] + g[u][j].cost;}}}}}}vector <int> patch, ThisPath;int MinCost = INT_MAX;void DFS(int v) {if (v == S) { //到达起点ThisPath.push_back(v);int ThisCost = 0;int ID = 0;int IDN = 0;for (int i = ThisPath.size() - 1; i > 0; i--) {ID = ThisPath[i];IDN = ThisPath[i - 1];for (int j = 0; j < g[ID].size(); j++) {if (g[ID][j].v == IDN)IDN = j;}ThisCost += g[ID][IDN].cost;}if (ThisCost < MinCost) {MinCost = ThisCost;patch = ThisPath;}ThisPath.pop_back();return;}ThisPath.push_back(v);for (int i = 0; i < pre[v].size(); i++) {DFS(pre[v][i]);}ThisPath.pop_back();}int main() {cin >> N >> M >> S >> D;isVis.resize(N, false);dis.resize(N,INT_MAX);cost.resize(N, INT_MAX);for (int i = 0; i < N; i++) {C[i] = INT_MAX;P[i] = -1;}int Head, Tail;Node temp;for (int i = 0; i < M; i++) {cin >> Head >> Tail >> temp.dis >> temp.cost;temp.v = Tail;g[Head].push_back(temp);temp.v = Head;g[Tail].push_back(temp);}#ifdef _DEBUGfor (int i = 0; i < N; i++) {for (int j = 0; j < g[i].size(); j++) { cout <<i << " " <<  g[i][j].v << " dis:" << g[i][j].dis << " cost:" << g[i][j].cost << endl;}}#endif//法一dijstra(S);DFS(D);for (int i = patch.size() - 1; i >= 0; i--) {cout << patch[i] << " ";}cout << dis[D] << " " << MinCost << endl;#ifdef _DEBUGfor (int i = 0; i < N; i++) {cout << "-------" << i << "--------" << endl;for (int j = 0; j < pre[i].size(); j++) {cout << pre[i][j] << endl;}}#endif//法二//stack <int> s;//int p = D;//while (p != -1) {//s.push(p);//p = P[p];//}//while (!s.empty()) {//cout << s.top() << " ";//s.pop();//}//cout << dis[D] << " " << C[D] << endl;system("pause");return 0;}

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