Wrong answer in SPOJ AKBAR

I applied BFS

algorithm is like this -

for each soldier I ran BFS from his source city and whichever city it protects I fill the source city as value in array cities. Initially all values are -1 , if a soldier protects the city say 'i', then cities[i] = source city of that soldier.

condition for No-

1. if a city is protected by two soldiers
2. if a city is left unprotected at the end

code is -

#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define io ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(0);
int main()
{
    int t,n,r,m,u,v,src,capacity;
    bool dec_capacity, invalid_flag;
    cin>>t;
    while(t--)
    {
        invalid_flag = 0;   // value = 1 -> NO , value = 0 -> YES
        cin>>n>>r>>m;
        ll cities[n+1];
        memset(cities, -1 , sizeof(cities));
        vector<ll> graph[n+1];
        for(ll i=0;i<r;i++)
        {
            cin>>u>>v;
            graph[u].push_back(v);
            graph[v].push_back(u);
        }
        vector< pair<ll,ll> > soldiers;
        for(ll i=0;i<m;i++)
        {
            cin>>u>>v;
            soldiers.push_back(make_pair(u,v));
        }
        queue<ll> q;
        for(ll i=0;i<m;i++)
        {
            src = soldiers[i].first;  // src city of soldier
            capacity = soldiers[i].second;
            if(cities[src]>0) // check if home city is already protected by another soldier
            {
                invalid_flag =1;
                break;
            }
            cities[src] = src;
            q.push(src);
            while(!q.empty())
            {
                u = q.front();
                q.pop();
                dec_capacity =0;
                if(capacity>0)
                {
                    for(ll j=0; j<graph[u].size();j++)
                    {
                        v = graph[u][j];
                        if(cities[v]>0 && cities[v]!=src) // if city is already protected by another soldier
                        {
                            invalid_flag = 1;
                            break;
                        }
                        if(cities[v]==-1)
                        {
                            dec_capacity =1;
                            q.push(v);
                            cities[v]=src;
                        }
                    }
                }
                if(invalid_flag)
                    break;
                if(dec_capacity)
                    capacity--;
            }
            if(invalid_flag)
                break;
        }
        // check if any city is left unprotected
        for(ll i=1;i<=n;i++)
        {
            if(cities[i]==-1)
            {
                invalid_flag=1;
                break;
            }
        }
        if(invalid_flag)
            cout<<"NO\n";
        else
            cout<<"YES\n";
    }
    return 0;
}