棰樼洰閾炬帴錛歨ttp://poj.org/problem?id=2387涓閬撶畝綆鍗曞崟鐨勬渶鐭礬鐨勯錛岄壌浜庢垜瀵逛簬spfa姣旇緝鐔熸倝錛屽氨鍐欎簡涓猻pfa錛岃繖涓ゅぉ鏋滄柇鐨勮鐔熸倝dijstra浠ュ強spfa鐨勫悇縐嶄紭鍖栥?/p>
榪欓亾棰樺紑濮嬶紝鍥捐鍏ラ棬鍩虹涔熷氨寮濮嬶紝鍙嶆閮芥槸鍒峰叆闂ㄥ熀紜錛岃屼笖鍋囨湡涔熷氨榪欎箞鐐瑰効鏃墮棿錛屽氨涓嶅繀鍒嗕粈涔堟椂鏈熷拰涓撻」浜嗭紝涓鏍蜂竴鏍風殑鏀諱笅鍘誨氨琛屻?br />
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1 #include <iostream>
2 #include <cstdio>
3 #include <cstdlib>
4 #include <cstring>
5 #include <cmath>
6 #include <algorithm>
7 #include <queue>
8 using namespace std;
9 #define N 10010
10 #define M 20010
11 int first[N], n, m, x, y, z, tot;
12 long g[N];
13 bool f[N];
14 struct edge{
15 int u, v, w, next;
16 }e[M];
17 queue<int> Q;
18 void init(){
19 for (int i = 0; i <= n; i++) g[i] = (1 << 30 - 1);
20 memset(f, 0, sizeof(f));
21 tot = 0; memset(first, 0, sizeof(first));
22 }
23 void add(int x, int y, int z){
24 tot++;
25 e[tot].u = x; e[tot].v = y; e[tot].w = z; e[tot].next = first[x]; first[x] = tot;
26 tot++;
27 e[tot].u = y; e[tot].v = x; e[tot].w = z; e[tot].next = first[y]; first[y] = tot;
28 }
29 void spfa(int st, int en){
30 f[st] = 1; Q.push(st); g[st] = 0;
31 while (!Q.empty()){
32 int now = Q.front();
33 f[now] = 0;
34 int i = first[now];
35 Q.pop();
36 while (i > 0){
37 if (g[e[i].v] > g[now] + e[i].w){
38 g[e[i].v] = g[now] + e[i].w;
39 if (!f[e[i].v]){
40 f[e[i].v] = 1;
41 Q.push(e[i].v);
42 }
43 }
44 i = e[i].next;
45 }
46 }
47 }
48 int main(){
49 while (~scanf("%d%d", &m, &n)){
50 init();
51 while (m--){
52 scanf("%d%d%d", &x, &y, &z);
53 add(x, y, z);
54 }
55 spfa(n, 1);
56 printf("%ld\n", g[1]);
57 }
58 return 0;
59 }
60
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