poj3159 差分约束 spfa

  1 //Accepted    2692 KB    1282 ms
  2 //差分约束 -->最短路
  3 //TLE到死，加了输入挂，手写queue
  4 #include <cstdio>
  5 #include <cstring>
  6 #include <iostream>
  7 #include <queue>
  8 #include <cmath>
  9 #include <algorithm>
 10 using namespace std;
 11 /**
 12   * This is a documentation comment block
 13   * 如果有一天你坚持不下去了，就想想你为什么走到这儿！
 14   * @authr songt
 15   */
 16 const int imax_n = 30005;
 17 const int imax_e = 150005;
 18 const int inf = 0x3f3f3f3f;
 19 struct node
 20 {
 21     int u,v,c;
 22     node(int u=0,int v=0,int c=0):u(u),v(v),c(c)
 23     {
 24 
 25     }
 26 }p[imax_e];
 27 int e=0;
 28 int head[imax_n];
 29 int next[imax_e];
 30 int dis[imax_n];
 31 bool vis[imax_n];
 32 int n,m;
 33 void addEdge(int u,int v,int c)
 34 {
 35     //p[e]=node(u,v,c);
 36     p[e].u=u;
 37     p[e].v=v;
 38     p[e].c=c;
 39     next[e]=head[u];
 40     head[u]=e++;
 41 }
 42 bool relax(int u,int v,int c)
 43 {
 44     if (dis[v]>dis[u]+c)
 45     {
 46         dis[v]=dis[u]+c;
 47         return true;
 48     }
 49     return false;
 50 }
 51 void init()
 52 {
 53     memset(head,-1,(n+2)*sizeof(head[0]));
 54     memset(next,-1,(n+2)*sizeof(next[0]));
 55     e=0;
 56 }
 57 //queue<int > q;
 58 int q[imax_e];
 59 int top;
 60 void spfa(int src)
 61 {
 62     //while (!q.empty()) q.pop();
 63     //memset(vis,0,(n+2)*sizeof(vis[0]));
 64     for (int i=1;i<=n;i++)
 65     {
 66         dis[i]=inf;
 67         vis[i]=0;
 68     }
 69     dis[src]=0;
 70     //q.push(src);
 71     top=1;
 72     q[0]=src;
 73     vis[src]=true;
 74     while (top)
 75     {
 76         //int pre=q.front();
 77         //q.pop();
 78         int pre=q[--top];
 79 
 80         vis[pre]=false;
 81         for (int i=head[pre];i+1;i=next[i])
 82         {
 83             if (relax(pre,p[i].v,p[i].c) && !vis[p[i].v])
 84             {
 85                 vis[p[i].v]=true;
 86                 //q.push(p[i].v);
 87                 q[top++]=p[i].v;
 88             }
 89         }
 90     }
 91 }
 92 /**
 93  * 读取一个int
 94  */
 95 inline int read_int()
 96 {
 97     int ret=0;
 98     char tmp;
 99     while(!isdigit(tmp=getchar()));
100     do{
101         ret=(ret<<3)+(ret<<1)+tmp-‘0‘;
102     }while(isdigit(tmp=getchar()));
103     return ret;
104 }
105 
106 int main()
107 {
108     //while (scanf("%d%d",&n,&m)!=EOF)
109     scanf("%d%d",&n,&m);
110     {
111         init();
112         int u,c,v;
113         for (int i=0;i<m;i++)
114         {
115             u=read_int();
116             v=read_int();
117             c=read_int();
118             addEdge(u,v,c);
119         }
120         spfa(1);
121         printf("%d\n",dis[n]);
122     }
123     return 0;
124 }