D - Silver Cow Party——最短路_spfa()算法

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>

using namespace std;

const int inf = 0x3f3f3f3f;
const int N = 1e3 + 4;

int n, e1

, e2

, dis
, vis
;

void spfa(int x, int e

);

int main(){
int m, i, x, u, v, w, sum
, mav;
scanf("%d %d %d", &n, &m, &x);
mav = 0;
memset(sum, 0, sizeof(sum));
memset(e1, inf, sizeof(e1));
memset(e2, inf, sizeof(e2));
for(i = 0; i < m; i++){
scanf("%d %d %d", &u, &v, &w);
e1[u][v] = w;
e2[v][u] = w;
}
spfa(x, e1);
for(i = 1; i <= n; i++)
sum[i] += dis[i];

spfa(x, e2);
for(i = 1; i <= n; i++){
mav = max(mav, sum[i]+dis[i]);
}
printf("%d\n", mav);
return 0;
}
void spfa(int x, int e

){
queue <int> q;
memset(dis, inf, sizeof(dis));
memset(vis, 0, sizeof(vis));
dis[x] = 0, vis[x] = 1;
q.push(x);
while(!q.empty()){
int t1 = q.front();
q.pop();
vis[t1] = 0;
for(int i = 1; i <= n; i++){
if(dis[t1] + e[t1][i] < dis[i]){
dis[i] = dis[t1] + e[t1][i];
if(!vis[i]){
q.push(i);
vis[i] = 1;
}
}
}
}
}