ural 1039. Anniversary party

ural 1039. Anniversary party

#include < iostream >
using   namespace  std;

int  N;
int  root;
int  val[ 6010 ];
int  chd[ 6010 ],now[ 6010 ],pre[ 6010 ],f0[ 6010 ],f1[ 6010 ];
inline  int  max( int  x, int  y){
     return  x > y ? x:y;
}
void  treedp( int  x){
    f1[x] = val[x]; f0[x] = 0 ;
     while (now[x]){
        treedp(chd[now[x]]);
        f1[x] += f0[chd[now[x]]];
        f0[x] += max(f1[chd[now[x]]],f0[chd[now[x]]]);
        now[x] = pre[now[x]];
    }
}
int  main()
{
    scanf( " %d " , & N);
     for ( int  i = 1 ;i <= N; ++ i)
        scanf( " %d " , & val[i]);
     int  x,y;
    memset(now, 0 , sizeof (now));
    root = N * (N + 1 ) / 2 ;
     for ( int  i = 1 ;i < N; ++ i){
        scanf( " %d%d " , & x, & y);
        chd[i] = x;
        pre[i] = now[y];
        now[y] = i;
        root -= x;
    }
    scanf( " %d%d " , & x, & y);
    treedp(root);
    printf( " %d\n " ,max(f0[root],f1[root]));
     return   0 ;
}