计蒜客-2017 ACM-ICPC 亚洲区（乌鲁木齐赛区）网络赛-H-Skiing

题解

代码

#include <iostream>
#include <queue>
#include <cstring>

using namespace std;

const int MAXN = 1e4 + 7;
const int MAXM = 2e5 + 7;

int n, m, tol;
int dis[MAXN];
int vis[MAXN];
int head[MAXN];

struct Node
{
int v, w, next;
} st[MAXM];

void add_edge(int u, int v, int w)
{
st[tol].v = v;
st[tol].w = w;
st[tol].next = head[u];
head[u] = tol++;
}

void spfa(int s)
{
queue<int> q;
memset(dis, -1, sizeof(dis));
memset(vis, 0, sizeof(vis));
dis[s] = 0;
vis[s] = 1;
q.push(s);

while (!q.empty())
{
int u = q.front();
q.pop();
vis[u] = 0;
for (int i = head[u]; i != -1; i = st[i].next)
{
int v = st[i].v;
if (dis[v] < dis[u] + st[i].w)
{
dis[v] = dis[u] + st[i].w;
if (!vis[v])
{
q.push(v);
vis[v] = 1;
}
}
}
}
}

void init()
{
tol = 0;
memset(head, -1, sizeof(head));
}

int main()
{
int T;
scanf("%d", &T);

while (T--)
{
init();
scanf("%d%d", &n, &m);

int u, v, w;
for (int i = 0; i < m; i++)
{
scanf("%d%d%d", &u, &v, &w);
add_edge(u, v, w);
}
for (int i = 1; i <= n; i++)
{
add_edge(0, i, 0);
add_edge(i, n + 1, 0);
}
spfa(0);
printf("%d\n", dis[n + 1]);
}

return 0;
}