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题意
最短路
题解
SPFA
调试记录
无
#include <cstdio>
#include <cstring>
#include <queue>
#define maxn 50005
using namespace std;
struct node{
int to, next, l;
}e[maxn << 1];
int head[maxn], tot = 0;
void addedge(int u, int v, int l){
e[++tot].to = v, e[tot].next = head[u], e[tot].l = l;
head[u] = tot;
}
int dis[maxn];
bool inq[maxn];
void SPFA(){
memset(dis, 0x3f, sizeof dis);
dis[1] = 0;
queue <int> q; while (!q.empty()) q.pop();
q.push(1);
inq[1] = true;
while (!q.empty()){
int cur = q.front(); inq[cur] = false; q.pop();
for (int i = head[cur]; i; i = e[i].next){
if (dis[e[i].to] > dis[cur] + e[i].l){
dis[e[i].to] = dis[cur] + e[i].l;
if (!inq[e[i].to]){
q.push(e[i].to);
inq[e[i].to] = true;
}
}
}
}
}
int n, m;
int main(){
scanf("%d%d", &n, &m);
for (int u, v, l, i = 1; i <= m; i++){
scanf("%d%d%d", &u, &v, &l);
addedge(u, v, l);
addedge(v, u, l);
}
SPFA();
printf("%d\n", dis[n]);
return 0;
}