Common Subexpression Elimination UVA - 12219

图论的一道简单的题目，在进行实现的时候既要记录每个节点的信息，包括该节点所指向的右子树的节点同时也包括左子树的节点位置，以及当前节点当中所包含的字符的信息，同时利用一个Map来进行查询以及去重，具体实现见如下代码：

#include<iostream>
#include<vector>
#include<string>
#include<set>
#include<stack>
#include<queue>
#include<map>
#include<algorithm>
#include<cmath>
#include<iomanip>
#include<cstring>
#include<sstream>
#include<cstdio>
#include<deque>
using namespace std;

string express;

class Node{
public:
int hash, left, right;
string s;
bool operator< (const Node a) const{
if (hash != a.hash) return hash < a.hash;
else if (left != a.left) return left < a.left;
return right < a.right;
}
};

Node node[50005];
map<Node, int> dict;

class Solve{
public:
int amount;
int finish[50005];
int cur;

int parse(int& ind){
int id;
id = amount++;
Node& temp=node[id];
temp.left = temp.right = -1;
temp.hash = 0;
temp.s = "";
while (ind < express.size() && isalpha(express[ind])){
temp.hash = temp.hash * 27 + express[ind] - 'a' + 1;
temp.s += express[ind];
ind++;
}
if (express[ind] == '('){
ind++;
temp.left = parse(ind);
ind++;
temp.right = parse(ind);
ind++;
}
if (dict.count(temp) != 0){
id--;
amount--;
return dict[temp];
}
return dict[temp] = id;
}

void Print(int ind){
if (finish[ind] == cur){
cout << ind + 1;
}
else{
finish[ind] = cur;
cout << node[ind].s;
if (node[ind].left != -1){
cout << "(";
Print(node[ind].left);
cout << ",";
Print(node[ind].right);
cout << ")";
}
}
}

void Deal(){
cur++;
amount = 0;
int ind = 0;
int res=parse(ind);
Print(res);
cout << endl;
}
};

int main(){
int c;
cin >> c;
Solve a;
a.cur = 0;
memset(a.finish,0,sizeof(a.finish));
while (c--){
dict.clear();
cin >> express;
a.Deal();
}
}