UVA 297 Quadtrees

题目链接：https://vjudge.net/problem/UVA-297

题意摘自《算法禁赛入门经典》

题目大意

　　略。

分析

　　先递归建树，然后 dfs 求答案。

代码如下

#include <bits/stdc++.h>
using namespace std;
 
#define INIT() ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define Rep(i,n) for (int i = 0; i < (int)(n); ++i)
#define For(i,s,t) for (int i = (int)(s); i <= (int)(t); ++i)
#define rFor(i,t,s) for (int i = (int)(t); i >= (int)(s); --i)
#define ForLL(i, s, t) for (LL i = LL(s); i <= LL(t); ++i)
#define rForLL(i, t, s) for (LL i = LL(t); i >= LL(s); --i)
#define foreach(i,c) for (__typeof(c.begin()) i = c.begin(); i != c.end(); ++i)
#define rforeach(i,c) for (__typeof(c.rbegin()) i = c.rbegin(); i != c.rend(); ++i)
 
#define pr(x) cout << #x << " = " << x << "  "
#define prln(x) cout << #x << " = " << x << endl
 
#define LOWBIT(x) ((x)&(-x))
 
#define ALL(x) x.begin(),x.end()
#define INS(x) inserter(x,x.begin())
#define UNIQUE(x) x.erase(unique(x.begin(), x.end()), x.end())
#define REMOVE(x, c) x.erase(remove(x.begin(), x.end(), c), x.end()); // 删去 x 中所有 c 
#define TOLOWER(x) transform(x.begin(), x.end(), x.begin(),::tolower);
#define TOUPPER(x) transform(x.begin(), x.end(), x.begin(),::toupper);
 
#define ms0(a) memset(a,0,sizeof(a))
#define msI(a) memset(a,0x3f,sizeof(a))
#define msM(a) memset(a,-1,sizeof(a))

#define MP make_pair
#define PB push_back
#define ft first
#define sd second
 
template<typename T1, typename T2>
istream &operator>>(istream &in, pair<T1, T2> &p) {
    in >> p.first >> p.second;
    return in;
}
 
template<typename T>
istream &operator>>(istream &in, vector<T> &v) {
    for (auto &x: v)
        in >> x;
    return in;
}

template<typename T>
ostream &operator<<(ostream &out, vector<T> &v) {
    Rep(i, v.size()) out << v[i] << " \n"[i == v.size() - 1];
    return out;
}
 
template<typename T1, typename T2>
ostream &operator<<(ostream &out, const std::pair<T1, T2> &p) {
    out << "[" << p.first << ", " << p.second << "]" << "\n";
    return out;
}

inline int gc(){
    static const int BUF = 1e7;
    static char buf[BUF], *bg = buf + BUF, *ed = bg;
    
    if(bg == ed) fread(bg = buf, 1, BUF, stdin);
    return *bg++;
} 

inline int ri(){
    int x = 0, f = 1, c = gc();
    for(; c<48||c>57; f = c=='-'?-1:f, c=gc());
    for(; c>47&&c<58; x = x*10 + c - 48, c=gc());
    return x*f;
}

template<class T>
inline string toString(T x) {
    ostringstream sout;
    sout << x;
    return sout.str();
}

inline int toInt(string s) {
    int v;
    istringstream sin(s);
    sin >> v;
    return v;
}

//min <= aim <= max
template<typename T>
inline bool BETWEEN(const T aim, const T min, const T max) {
    return min <= aim && aim <= max;
}

typedef unsigned int uI;
typedef long long LL;
typedef unsigned long long uLL;
typedef vector< int > VI;
typedef vector< bool > VB;
typedef vector< char > VC;
typedef vector< double > VD;
typedef vector< string > VS;
typedef vector< LL > VL;
typedef vector< VI > VVI;
typedef vector< VB > VVB;
typedef vector< VS > VVS;
typedef vector< VL > VVL;
typedef vector< VVI > VVVI;
typedef vector< VVL > VVVL;
typedef pair< int, int > PII;
typedef pair< LL, LL > PLL;
typedef pair< int, string > PIS;
typedef pair< string, int > PSI;
typedef pair< string, string > PSS;
typedef pair< double, double > PDD;
typedef vector< PII > VPII;
typedef vector< PLL > VPLL;
typedef vector< VPII > VVPII;
typedef vector< VPLL > VVPLL;
typedef vector< VS > VVS;
typedef map< int, int > MII;
typedef unordered_map< int, int > uMII;
typedef map< LL, LL > MLL;
typedef map< string, int > MSI;
typedef map< int, string > MIS;
typedef multiset< int > mSI;
typedef set< int > SI;
typedef stack< int > SKI;
typedef deque< int > DQI;
typedef queue< int > QI;
typedef priority_queue< int > PQIMax;
typedef priority_queue< int, VI, greater< int > > PQIMin;
const double EPS = 1e-8;
const LL inf = 0x7fffffff;
const LL infLL = 0x7fffffffffffffffLL;
const LL mod = 1e9 + 7;
const int maxN = 1e4 + 7;
const LL ONE = 1;
const LL evenBits = 0xaaaaaaaaaaaaaaaa;
const LL oddBits = 0x5555555555555555;

struct QuadtreeNode {
    char type;
    int num;
    QuadtreeNode* nxt[4];
    
    QuadtreeNode(char tp) : type(tp) {
        Rep(i, 4) nxt[i] = nullptr;
    }
};

int N;
string str1, str2;
QuadtreeNode* root1 = nullptr;
QuadtreeNode* root2 = nullptr;

int build(QuadtreeNode* &rt, string &str, int p, int cnt) { // 要传指针的引用，不然建树的时候指针就不是树上的指针了 
    assert(p < str.size() && rt == nullptr);
    rt = new QuadtreeNode(str[p]);
    
    switch(str[p]) {
        case 'p':{
            ++p;
            rt->num = 0;
            Rep(i, 4) {
                p = build(rt->nxt[i], str, p, cnt >> 2);
                rt->num += rt->nxt[i]->num;
            }
            return p;
        }
        case 'f':{
            rt->num = cnt;
            return p + 1;
        }
        case 'e':{
            rt->num = 0;
            return p + 1;
        }
        default:{
            assert(false);
        }
    }
}

void clear(QuadtreeNode* &rt) {
    if(rt == nullptr) return;
    Rep(i, 4) {
        if(rt->nxt[i] != nullptr) {
            clear(rt->nxt[i]);
        }
    }
    delete rt;
    rt = nullptr;
}

int solve(QuadtreeNode* &rt1, QuadtreeNode* &rt2) {
    int ret = 0;
    
    if(rt1->type == 'p' && rt2->type == 'p') {
        Rep(i, 4) ret += solve(rt1->nxt[i], rt2->nxt[i]);
    }
    else ret = max(rt1->num, rt2->num);
    
    return ret;
}

int main() {
    //freopen("MyOutput.txt","w",stdout);
    //freopen("input.txt","r",stdin);
    //INIT();
    cin >> N;
    while(N--) {
        clear(root1);
        clear(root2);
        cin >> str1 >> str2;
        
        build(root1, str1, 0, 1024);
        build(root2, str2, 0, 1024);
        
        printf("There are %d black pixels.\n", solve(root1, root2));
    }
    return 0;
}