[题解]UVa 12661 Funny Car Racing - spfa

Posted 2020-08-28 阿波罗2003

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　　很简单的一道最短路问题。分情况处理赛道的打开和关闭。

Code

  1 /**
  2  * UVa
  3  * Problem#12661
  4  * Accepted
  5  * Time:50ms
  6  */
  7 #include<iostream>
  8 #include<fstream>
  9 #include<sstream>
 10 #include<cstdio>
 11 #include<cstdlib>
 12 #include<cstring>
 13 #include<ctime>
 14 #include<cctype>
 15 #include<cmath>
 16 #include<algorithm>
 17 #include<stack>
 18 #include<queue>
 19 #include<set>
 20 #include<map>
 21 #include<vector>
 22 using namespace std;
 23 typedef bool boolean;
 24 #define smin(a, b)    (a) = min((a), (b))
 25 #define smax(as, b)    (a) = max((a), (b))
 26 template<typename T>
 27 inline boolean readInteger(T& u){
 28     char x;
 29     int aFlag = 1;
 30     while(!isdigit((x = getchar())) && x != \'-\' && x != -1);
 31     if(x == -1)    return false;
 32     if(x == \'-\'){
 33         x = getchar();
 34         aFlag = -1;
 35     }
 36     for(u = x - \'0\'; isdigit((x = getchar())); u = (u << 3) + (u << 1) + x - \'0\');
 37     ungetc(x, stdin);
 38     u *= aFlag;
 39     return true;
 40 }
 41 
 42 typedef class Edge{
 43     public:
 44         int end;
 45         int next;
 46         int open;
 47         int close;
 48         int t;
 49         Edge(const int end = 0, const int next = 0, const int open = 0, const int close = 0, const int t = 0):end(end), next(next), open(open), close(close), t(t){        }
 50         int across(int arrived){
 51             int re = arrived % (open + close);
 52             if(re >= 0 && re + t <= open)    return     arrived + t;
 53             return (arrived / (open + close) + 1) * (open + close) + t;
 54         }
 55 }Edge;
 56 
 57 typedef class MapManager{
 58     public:
 59         int ce;
 60         Edge* edges;
 61         int* h;
 62         MapManager():ce(0), edges(NULL), h(NULL){        }
 63         MapManager(int points, int limit):ce(0){
 64             h = new int[(const int)(points + 1)];
 65             edges = new Edge[(const int)(limit + 1)];
 66             memset(h, 0, sizeof(int) * (points + 1));
 67         }
 68         inline void addEdge(int from, int end, int open, int close, int t){
 69             if(t > open)    return;        //无法通过 
 70             edges[++ce] = Edge(end, h[from], open, close, t);
 71             h[from] = ce;
 72         }
 73         Edge& operator [](int pos){
 74             return edges[pos];
 75         }
 76         void clear(){
 77             delete[] edges;
 78             delete[] h;
 79             ce = 0;
 80         }
 81 }MapManager;
 82 
 83 #define m_begin(g, i)    (g).h[(i)]
 84 
 85 int n, m, from, _end;
 86 MapManager g;
 87 
 88 inline boolean init(){
 89     if(!readInteger(n))    return false;
 90     readInteger(m);
 91     readInteger(from);
 92     readInteger(_end);
 93     g = MapManager(n, m);
 94     for(int i = 1, u, v, a, b, t; i <= m; i++){
 95         readInteger(u);
 96         readInteger(v);
 97         readInteger(a);
 98         readInteger(b);
 99         readInteger(t);
100         g.addEdge(u, v, a, b, t);
101     }
102     return true;
103 }
104 
105 boolean* visited;
106 queue<int>    que;
107 int* f;
108 inline int spfa(int s, int t){
109     que.push(s);
110     visited[s] = true;
111     f[s] = 0;
112     while(!que.empty()){
113         int e = que.front();
114         que.pop();
115         visited[e] = false;
116         for(int i = m_begin(g, e); i != 0; i = g[i].next){
117             int& eu = g[i].end;
118             int cmp = g[i].across(f[e]);
119             if(cmp < f[eu]){
120                 f[eu] = cmp;
121                 if(!visited[eu] && eu != t){
122                     que.push(eu);
123                     visited[eu] = true;
124                 }
125             }
126         }
127     }
128     return f[t];
129 }
130 
131 inline void solve(){
132     visited = new boolean[(const int)(n + 1)];
133     f = new int[(const int)(n + 1)];
134     memset(visited, false, sizeof(boolean) * (n + 1));
135     memset(f, 0x7f, sizeof(int) * (n + 1));
136     int res = spfa(from, _end);
137     printf("%d\\n", res);
138 }
139 
140 inline void clear(){
141     g.clear();
142     delete[] visited;
143     delete[] f;
144 }
145 
146 int main(){
147     int kase = 1;
148     while(init()){
149         printf("Case %d: ", kase++);
150         solve();
151         clear();
152     }
153     return 0;
154 }