WA on Sub1 #1#3 求条

#include<bits/stdc++.h>
using namespace std;
int T,n,m,u,v,ww,dis[105],cnt[105],flag[105],q[105],head,tail,ans;
vector<int>g[105];
vector<int>w[105];
int main()
{
    cin>>T;
    while(T--)
    {
        cin>>n>>m;
        for(int i=1;i<=n+2;i++)g[i].clear(),w[i].clear();
        for(int i=1;i<=m;i++)
        {
            cin>>u>>v>>ww;
            g[u].push_back(v+1);
            w[u].push_back(ww);
            g[v+1].push_back(u);
            w[v+1].push_back(-ww);
        }
        n++;
        for(int i=1;i<=n;i++)
        {
            g[n+1].push_back(i);
            w[n+1].push_back(0);
        }
        memset(cnt,0,(n<<2)+10);
        memset(flag,0,(n<<2)+10);
        memset(dis,0x3f,(n<<2)+10);
        dis[1]=0,flag[1]=cnt[1]=1;
        head=0,tail=1,q[1]=1,ans=1;
        while((head^tail)&&ans)
        {
            head=head%(n+1)+1;
            flag[q[head]]^=1;
            for(int i=0;i<g[q[head]].size();i++)
            if(dis[q[head]]+w[q[head]][i]<dis[g[q[head]][i]])
            {
                dis[g[q[head]][i]]=dis[q[head]]+w[q[head]][i];
                if(!flag[g[q[head]][i]])
                {
                    flag[g[q[head]][i]]^=1;
                    tail=tail%(n+1)+1;
                    q[tail]=g[q[head]][i];
                    cnt[q[tail]]++;
                    if(cnt[q[tail]]>=n+2)ans=0;
                }
            }
        }
        cout<<(ans?"true\n":"false\n");
    }
    return 0;
}