POJ 3169 差分约束

只要建立成d[u] <= d[v] + w;求最短路即可

图不连通输出-2

有负环输出-1

#include <set>#include <map>#include <cmath>#include <queue>#include <stack>#include <string>#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>using namespace std;typedef  long long LL;const double PI = acos(-1.0);template <class T> inline  T MAX(T a, T b){if (a > b) return a;return b;}template <class T> inline  T MIN(T a, T b){if (a < b) return a;return b;}const int N = 111;const int M = 11111;const LL MOD = 1000000007LL;const int dir[4][2] = {1, 0, -1, 0, 0, -1, 0, 1};const int INF = 0x3f3f3f3f;struct node{    int v, next, w;}edge[55555];int dist[11111], inq[11111], vis[11111];int head[11111], cnt;int n, ml, md;inline void addnode(int u, int v, int w){    edge[cnt].v = v; edge[cnt].w = w;    edge[cnt].next = head[u]; head[u] = cnt++;}int spfa(){    fill(dist, dist + 1 + n, INF);    memset(inq, 0, sizeof(inq));    memset(vis, 0, sizeof(vis));    queue < int > q;    int i, j, k, u, v, w;    inq[1] = 1; dist[1] = 0; vis[1] = 1;    q.push(1);    while (!q.empty())    {        u = q.front(); q.pop(); inq[u]--;        for (i = head[u]; ~i; i = edge[i].next)        {            v = edge[i].v; w = edge[i].w;            if (dist[u] + w < dist[v])            {                dist[v] = dist[u] + w;                if (!inq[v])                {                    inq[v]++; vis[v]++; q.push(v);                    if (vis[v] > n) return -1;                }            }        }    }    return 1;}int main(){    while (scanf("%d%d%d", &n, &ml, &md) != EOF)    {        int i, j, k, u, v, w;        memset(head, -1, sizeof(head));        cnt = 0;        for (i = 0; i < ml; ++i)        {            scanf("%d%d%d", &u, &v, &w);            if (u > v) {k = u; u = v; v = k;}            addnode(u, v, w);        }        for (i = 0; i < md; ++i)        {            scanf("%d%d%d", &u, &v, &w);            if (u > v) {k = u; u = v; v = k;}            addnode(v, u, -w);        }        for (i = 0; i < n; ++i)            addnode(i + 1, i, 0);        int ans = spfa();        if (ans == -1) printf("-1\n");        else if (dist[n] == INF) printf("-2\n");        else printf("%d\n", dist[n]);    }    return 0;}