pku3169 Layout

http://poj.org/problem?id=3169

图论，差分约束系统，SPFA

#include <stdio.h>
#include <string.h>
#include <queue>
#define N 1234

using namespace std;

int n, m, src;
vector<pair<int, int> > g[N];
int dist[N];
bool inQue[N];
queue<int> que;
int count[N];
const int inf = 1<<29;

int spfa()
{
    int i;
    for(i=0; i<N; i++)
    {
        dist[i] = inf;
        count[i] = 0;
    }
    dist[src] = 0;
    while(!que.empty())
    {
        que.pop();
    }
    que.push(src);
    count[src] ++;
    inQue[src] = true;
    while(!que.empty())
    {
        int u = que.front();
        que.pop();
        for(i=0; i<g[u].size(); i++)
        {
            if(dist[u] + g[u][i].second < dist[g[u][i].first])
            {
                dist[g[u][i].first] = dist[u] + g[u][i].second;
                if(!inQue[g[u][i].first])
                {
                    inQue[g[u][i].first] = true;
                    que.push(g[u][i].first);
                    count[g[u][i].first] ++;
                    if(count[g[u][i].first] > n)
                    {
                        return -1;
                    }
                }
            }
        }
        inQue[u] = false;
    }
    if(dist[n] == inf)
    {
        return -2;
    }
    return dist[n];
}


int main()
{
    int i, j, m1, m2, x, y, len;
    int temp;
    scanf("%d%d%d", &n, &m1, &m2);
    for(i=1; i<=m1; i++)
    {
        scanf("%d%d%d", &x, &y, &len);
        if(y < x)
        {
            temp = x, x = y, y = temp;
        }
        g[x].push_back(make_pair(y, len));
    }
    for(i=1; i<=m2; i++)
    {
        scanf("%d%d%d", &x, &y, &len);
        if(y < x)
        {
            temp = x, x = y, y = temp;
        }
        g[y].push_back(make_pair(x, -len));
    }
    src = 1;
    printf("%d\n", spfa());
    return 0;
}