Spoj Total Flow

#include <ctime>
#include <algorithm>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <cstdio>
#include <cstdlib>
#include <cctype>
#include <cmath>
using namespace std;
typedef long long LL;
#define FOR(k,a,b) for(int k(a); k < (b); ++k)
#define REP(k,a) for(int k=0; k < (a); ++k)

int calc(char c)
{
    if(c>='A' && c<='Z')
        return c-'A';
    return c-'a'+'Z'-'A'+1;
}

int main()
{
    int N,c,S=0,T='Z'-'A',maxflow=0,o,mxo;
    char a,b;
    cin >> N;
    const int R=('Z'-'A'+1)*2;
    int cap[R][R],res[R][R],act[R][R],visited[R];
    deque<int> q;
    memset(cap,0,sizeof(cap));
    memset(act,0,sizeof(act));
    REP(i,N)
    {
        cin >> a >> b >> c;
        cap[calc(a)][calc(b)]+=c;
    }
    while(true)
    {
        //calculate residual
        memset(res,0,sizeof(res));
        REP(i,R)
        REP(j,R)
        {
            res[i][j]+=cap[i][j]-act[i][j];
            res[j][i]+=act[i][j];
        }
        //bfs find shortest augment path
        memset(visited,-1,sizeof(visited));
        q.push_back(0);
        visited[0]=0;
        while(q.size())
        {
            o=q.front();
            q.pop_front();
            REP(i,R)
            {
                if(visited[i]!=-1 || res[o][i]==0)
                    continue;
                visited[i]=o;
                if(i==T)
                {
                    q.clear();
                    break;
                }
                else
                    q.push_back(i);
            }
        }
        //calculate maximum
        o=T;
        mxo=((int)1e9);
        while(o>0)
        {
            mxo=min(mxo,res[visited[o]][o]);
            o=visited[o];
        }
        if(visited[T]==-1 || mxo==0)
            break;
        maxflow+=mxo;
        o=T;
        while(o>0)
        {
            act[visited[o]][o]+=mxo;
            o=visited[o];
        }
    }
    cout << maxflow << endl;
    return 0;
}