先对所有点做bfs求出任意两点间最短距离,然后暴力枚举中转点i,j求出答案。。。。
#include <iostream>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <bitset>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <climits>
#include <cstdlib>
#include <cmath>
#include <time.h>
#define maxn 3005
#define maxm 10005
#define eps 1e-12
#define mod 998244353
#define INF 0x3f3f3f3f
#define PI (acos(-1.0))
#define lowbit(x) (x&(-x))
#define mp make_pair
#define ls o<<1
#define rs o<<1 | 1
#define lson o<<1, L, mid
#define rson o<<1 | 1, mid+1, R
#pragma comment(linker, "/STACK:102400000,102400000")
#define pii pair<int, int>
typedef long long LL;
typedef unsigned long long ULL;
//typedef int LL;
using namespace std;
LL qpow(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base;base=base*base;b/=2;}return res;}
LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}
// head
struct Edge
{
int v;
Edge *next;
}*H[maxn], E[maxm], *edges;
queue<pii> q;
int dis[maxn][maxn];
int n, m, ans;
void addedges(int u, int v)
{
edges->v = v;
edges->next = H[u];
H[u] = edges++;
}
void init()
{
edges = E;
memset(H, 0, sizeof H);
memset(dis, INF, sizeof dis);
}
void bfs(int now)
{
q.push(mp(now, 0));
while(!q.empty()) {
int u = q.front().first, dist = q.front().second;
q.pop();
if(dis[now][u] != INF) continue;
dis[now][u] = dist;
for(Edge *e = H[u]; e; e = e->next) {
int v = e->v;
if(dist + 1 < dis[now][v])
q.push(mp(v, dist + 1));
}
}
}
void calc(int s0, int t0, int l0, int s1, int t1, int l1)
{
for(int i = 1; i <= n; i++)
for(int j = 1; j <= n; j++)
if(dis[s0][i] + dis[i][j] + dis[j][t0] <= l0)
if(dis[s1][i] + dis[i][j] + dis[j][t1] <= l1)
ans = min(ans, dis[s0][i] + dis[j][t0] + dis[s1][i] + dis[j][t1] + dis[i][j]);
}
void work()
{
int u, v, cnt = 0;
for(int i = 1; i <= m; i++) {
scanf("%d%d", &u, &v);
addedges(u, v);
addedges(v, u);
cnt++;
}
for(int i = 1; i <= n; i++) bfs(i);
int s0, t0, l0, s1, t1, l1;
scanf("%d%d%d", &s0, &t0, &l0);
scanf("%d%d%d", &s1, &t1, &l1);
ans = INF;
if(dis[s0][t0] <= l0 && dis[s1][t1] <= l1) ans = dis[s0][t0] + dis[s1][t1];
else {
printf("-1\n");
return;
}
calc(s0, t0, l0, s1, t1, l1);
calc(t0, s0, l0, s1, t1, l1);
printf("%d\n", cnt - ans);
}
int main()
{
while(scanf("%d%d", &n, &m)!=EOF) {
init();
work();
}
return 0;
}