POJ3159 dijkstra+ adjacency table + priority queue

today I learned a new posture, using adjacency table + priority queue to optimize Dijkstra, so that time complexity from O (n^2+e) to O (nlogn+e), mom no longer have to worry about my timeout! ~\ (^o^)/

Candies

Time Limit: 1500MS		Memory Limit: 131072K
Total Submissions: 25077		Accepted: 6810

Description

During The Kindergarten days, Flymouse is the monitor of his class. Occasionally the head-teacher brought the kids of Flymouse ' s Class A large bag of candies and had flymouse distribute them . All the kids loved candies very much and often compared the numbers for candies they got with others. A kid A could had the idea that though it might is the case that another kid B is better than him in some aspect and ther Efore had a reason for deserving more candies than he did, he should never get a certain number of candies fewer than B di D no matter how many candies he actually got, otherwise he would feel dissatisfied and go to the head-teacher to complain About Flymouse ' s biased distribution.

Snoopy shared class with Flymouse at that time. Flymouse always compared the number of he candies with that of Snoopy ' s. He wanted to make the difference between the numbers as large as possible while keeping every kid satisfied. Now he had just got another bag of candies from the Head-teacher, what is the largest difference he could make out of it?

Input

The input contains a single test cases. The test cases starts with a line with both integers N and M not exceeding and respectivel Y. N is the number of kids in the class and the kids were numbered 1 throughN. Snoopy and Flymouse were always numbered 1 and N. Then follow M lines each holding three integers A, B and C in order, meaning that kid A believed that kid B should never get over C candies more than he did.

Output

Output one line with only the largest difference desired. The difference is guaranteed to be finite.

Sample Input

2 21 2 52 1 4

Sample Output

5

1#include <iostream>2#include <cstdio>3#include <cstring>4#include <algorithm>5#include <queue>6#include <vector>7 using namespacestd;8 #defineINF 0x7fffffff9 structnodeTen { One     intk,w; A }; - BOOL operator< (ConstNode &t1,ConstNode &T2) - { the     returnT1.w>T2.W; - } -Priority_queue<node>Q; - BOOLvis[30010]; +vector<vector<node> >v; - intMain () + { A     intn,m,i,j,a,b,c; at node p; -      while(~SCANF ("%d%d",&n,&m)) -     { - v.clear (); -V.resize (n+1); -memset (Vis,0,sizeof(Vis)); in          for(i=0; i<m;i++) -         { toscanf"%d%d%d",&a,&b,&c); +p.k=b; -p.w=C; the V[a].push_back (p); *         } $p.k=1;Panax Notoginsengp.w=0; - Q.push (p); the          while(!q.empty ()) +         { Ap=q.top (); the Q.pop (); +             if(VIS[P.K]) -                 Continue; $vis[p.k]=true; $             if(p.k==N) -                  Break; -              for(i=0; I<v[p.k].size (); i++) the             { - node S;Wuyis.k=V[P.K][I].K; the                 if(VIS[S.K])Continue; -s.w=p.w+V[P.K][I].W; Wu Q.push (s); -             } About         } $printf"%d\n", P.W); -     } -     return 0; -}

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POJ3159 dijkstra+ adjacency table + priority queue