poj 2387 Til the Cows Come Home

裸的最短路

spfa 水过

#include<stdio.h>#include<string.h>#include<queue>#define INF 0x3f3f3f3f#define MAXN 10001using namespace std;struct edge{int u, v, w, next;}e[MAXN];int first[MAXN], dist[MAXN], ecnt;bool inq[MAXN];int t, n, a, b, c;void spfa(){queue<int> que;memset(inq, false,sizeof(inq));for(int i = 0; i <= n; ++i)dist[i] = (i == n ? 0 : INF);que.push(n);while(!que.empty()){int x = que.front();que.pop();inq[x] = false;for(int i = first[x]; i != -1; i = e[i].next){if(dist[e[i].v] - dist[x] > e[i].w){dist[e[i].v] = dist[x] + e[i].w;if(!inq[e[i].v]){inq[e[i].v] = true;que.push(e[i].v);}}}}}int main(){scanf("%d%d",&t, &n);memset(first, -1, sizeof(first));for(int i = 0, ecnt = 0; i < t; ++i){scanf("%d%d%d",&e[ecnt].u, &e[ecnt].v, &e[ecnt].w);e[ecnt].next = first[e[ecnt].u];first[e[ecnt].u] = ecnt;ecnt++;e[ecnt].u = e[ecnt - 1].v;e[ecnt].v = e[ecnt - 1].u;e[ecnt].w = e[ecnt - 1].w;e[ecnt].next = first[e[ecnt].u];first[e[ecnt].u] = ecnt;ecnt++;}/*from landmark N to landmark 1*/spfa();printf("%d/n",dist[1]);return 0;}