畅通工程续hdu-1874

Problem Description

某省自从实行了很多年的畅通工程计划后,终于修建了很多路。不过路多了也不好,每次要从一个城镇到另一个城镇时,都有许多种道路方案可以选择,而某些方案要比另一些方案行走的距离要短很多。这让行人很困扰。现在,已知起点和终点,请你计算出要从起点到终点,最短需要行走多少距离。

 

Input

本题目包含多组数据,请处理到文件结束。
每组数据第一行包含两个正整数N和M(0

 

Output

对于每组数据,请在一行里输出最短需要行走的距离。如果不存在从S到T的路线,就输出-1.

 

Sample Input

3 3 0 1 1 0 2 3 1 2 1 0 2 3 1 0 1 1 1 2

 

Sample Output

2 -1

这道题可以用dijkstra来写,然后由于是双向图,所以存图的时候要存两次!!!!

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#define INF 0x3f3f3f3f
#define mem memset
#define sc scanf
#define pr printf
typedef long long ll;
using namespace std;
//inline int read(){
//    int X = 0, w = 0; char ch = 0;
//    while (!isdigit(ch)) { w |= ch == '-'; ch = getchar(); }
//    while (isdigit(ch)) X = (X << 3) + (X << 1) + (ch ^ 48), ch = getchar();
//    return w ? -X : X;
//}
//inline double dbread(){
//    double X = 0, Y = 1.0; int w = 0; char ch = 0;
//    while (!isdigit(ch)) { w |= ch == '-'; ch = getchar(); }
//    while (isdigit(ch)) X = X * 10 + (ch ^ 48), ch = getchar();
//    ch = getchar();//读入小数点
//    while (isdigit(ch)) X += (Y /= 10) * (ch ^ 48), ch = getchar();
//    return w ? -X : X;
//}
//inline void write(int x){
//    if (x < 0) putchar('-'), x = -x;
//    if (x > 9) write(x / 10);
//    putchar(x % 10 + '0');
//}
#define maxn 210
struct Edge {
    int from, to, dist;
    Edge(int f, int t, int d) : from(f), to(t), dist(d) {}
 };
struct HeapNode {
    int d, u;
    bool operator< (const HeapNode& rhs) const {
        return d > rhs.d;
    }
    HeapNode(int D, int U) :d(D), u(U) {}
};
struct Dijkstra {
    int n, m;
    vector edges;
    vector G[maxn];
    bool done[maxn];
    int d[maxn];
    int p[maxn];
    void init(int n) {
        this->n = n;
        for (int i = 0; i < n; ++i)
            G[i].clear();
        edges.clear();
    }
    void addedge(int from, int to, int dist) {
        edges.push_back(Edge(from, to, dist));
        m = edges.size();
        G[from].push_back(m - 1);
    }
    int dijkstra(int s, int e) {
        priority_queue Q;
        for (int i = 0; i < n; ++i)
            d[i] = INF;
        d[s] = 0;
        mem(done, 0, sizeof(done));
        Q.push(HeapNode(0, s));
        while (!Q.empty()) {
            HeapNode x = Q.top();
            Q.pop();
            int u = x.u;
            if (done[u])
                continue;
            done[u] = true;
            for (int i = 0; i < G[u].size(); ++i) {
                Edge& e = edges[G[u][i]];
                if (d[e.to] > d[u] + e.dist) {
                    d[e.to] = d[u] + e.dist;
                    p[e.to] = G[u][i];
                    Q.push(HeapNode(d[e.to], e.to));
                }
            }
        }
        return d[e];
    }
}DK;
int n, m;
int s, e, d;
int main(){
    ios::sync_with_stdio(false);
    while (cin >> n >> m && n != -1 && m != -1) {
        DK.init(n);
        for (int i = 0; i < m; ++i) {
            cin >> s >> e >> d;
            DK.addedge(s, e, d);
            DK.addedge(e, s, d);
        }
        cin >> s >> e;
        int len = DK.dijkstra(s, e);
        if (len == INF) cout << -1 << endl;
        else cout << len << endl;
    }
    return 0;
}

 

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