1003. Emergency 解析

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这道题的坑点在于：

一、图为无向图，在用邻接表存储图的时候，我把图默认当成有向图了。导致有两个不能AC。改了就OK了~

二、Dijstra算法的进一步应用。这个我理解的还不透彻，瞎说下。

首先是进行一个大的循环，以顶点数为次数，保证循环完整个图。

然后是对dist数组进行筛选选出最小的顶点号u

然后遍历与u相邻的结点记为v 计算以u为中间点到v的距离会不会缩短。

边计算边累加边数和权重。（这里思想比较特别需要好好理解）

路径个数：路径更短：v=u的路径数

路径一样：v=u+v的路径数

权重：v的权重=v+u

附上AC代码（加了一些用不到的功能练手用的）

#include <iostream>#include <vector>#include <fstream>#include <climits>#define N 500#define inf INT_MAX;using namespace std;struct Node{int v;int e;Node(int _v, int _e) :v(_v), e(_e) {};};struct Head{int weight;vector<Node> *p;Head(int _w, vector<Node> * _p) : weight(_w), p(_p) {};};vector<Node> Link[N];//邻接表vector<Head> G;//邻接表头void  CreateGrap(int V , int E , int &start ,int &end ) {int weight;int h, e, w;for (int i = 0; i < V; i++) {cin >> weight;G.push_back(Head(weight, &Link[i]));}for (int i = 0; i < E; i++) {cin >> h >> e >> w;Link[h].push_back(Node(e, w));Link[e].push_back(Node(h, w));}}//void printarry(int V, int * dist, int * pre, int * sum, int * weig, bool * visit) {//检测函数值//cout << "======dist=====" << endl;//for (int i = 0; i < V; i++)//cout << dist[i] << " ";//cout << endl;//cout << "===============" << endl;////cout << "======weig=====" << endl;//for (int i = 0; i < V; i++)//cout << weig[i] << " ";//cout << endl;//cout << "===============" << endl;////cout << "======sum=====" << endl;//for (int i = 0; i < V; i++)//cout << sum[i] << " ";//cout << endl;//cout << "===============" << endl;////cout << "======pre=====" << endl;//for (int i = 0; i < V; i++)//cout << pre[i] << " ";//cout << endl;//cout << "===============" << endl;//}int Dijistra(int start,int V, int * dist, int * pre, int * sum, int * weig, bool * visit) {dist[start] = 0;//起始点距离为0sum[start] = 1;weig[start] = G[start].weight;for (int i = 0; i < V; i++) { //全连通域 循环无iint u = -1, MIN = inf;for (int j = 0; j < V; j++) {//第一个必为起始点且为0，与之相邻的边的权重等于distif (!visit[j] && dist[j] < MIN) { //找最小dist点u = j;MIN = dist[j];}}if (u == -1) return 0; //不联通visit[u] = true;for (int j = 0; j < (*G[u].p).size(); j++) { //u的邻接点int v = (*G[u].p)[j].v; //u为中间点if (!visit[v] && dist[u] + (*G[u].p)[j].e < dist[v]) {dist[v] = dist[u] + (*G[u].p)[j].e;sum[v] = sum[u];weig[v] = weig[u] + G[v].weight;pre[v] = u;//printarry(V, dist, pre, sum, weig, visit);}else if (dist[u] + (*G[u].p)[j].e == dist[v]) {if (weig[v] < weig[u] + G[v].weight) {weig[v] = weig[u] + G[v].weight;pre[u] = pre[v];}sum[v] += sum[u];//printarry(V, dist, pre, sum, weig, visit);}}}}int main(){int V, E;int start, end;cin >> V >> E >> start >> end;int * dist = new int[V];int * pre = new int[V];bool * visit = new bool[V];int * sum = new int[V];int * weig = new int[V];for (int i = 0; i < V; i++) {dist[i] = inf;pre[i] = -1;visit[i] = false;sum[i] = 0;weig[i] = 0;}CreateGrap(V,E,start,end);Dijistra(start, V, dist, pre, sum, weig, visit);cout << sum[end] << " " << weig[end] << endl;system("pause");delete [] dist;delete [] pre;delete [] sum;delete[] visit;delete[] weig;return 0;}

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