USACO Section 2.3: Zero Sum

这题我做得比较麻烦，网上有个比较简单的程序。

 /*
 ID: yingzho1
 LANG: C++
 TASK: zerosum
 */
 #include <iostream>
 #include <fstream>
 #include <string>
 #include <map>
 #include <vector>
 #include <set>
 #include <algorithm>
 #include <stdio.h>
 #include <queue>
 #include <cstring>
 #include <cmath>

 using namespace std;

 ifstream fin("zerosum.in");
 ofstream fout("zerosum.out");

 int N;
 set<string> res;

 string intToString(int n) {
     string ret;
     ) ";
     while (n) {
         );
         ret += tmp;
         n /= ;
     }
     reverse(ret.begin(), ret.end());
     string res;
     res += ret[];
     ; i < ret.size(); i++) res = res + ' ' + ret[i];
     return res;
 }

 bool check(vector<int> &num, vector<char> &op) {
     ) return false;
     ];
     ; i < num.size(); i++) {
         ] == '+') sum += num[i];
         else sum -= num[i];
     }
     ;
 }

 void dfs(int dep, vector<int> &num, vector<char> &op, int sum) {
     if (dep > N) {
         /*for (int i = 0; i < num.size(); i++) cout << num[i] << " ";
         cout << endl;
         for (int i = 0; i < op.size(); i++) cout << op[i] << " ";
         cout << endl;*/
         if (sum) num.push_back(sum);
         if (check(num, op)) {
             string tmp;
             ; i < num.size()-; i++) {
                 tmp = tmp + intToString(num[i]) + op[i];
             }
             tmp = tmp + intToString(num[num.size()-]);
             res.insert(tmp);
         }
         if (sum) num.pop_back();
         return;
     }
     sum = sum* + dep;
     dfs(dep+, num, op, sum);
     num.push_back(sum);
     op.push_back('+');
     dfs(dep+, num, op, );
     op.pop_back();
     op.push_back('-');
     dfs(dep+, num, op, );
     op.pop_back();
     num.pop_back();
 }

 int main()
 {
     fin >> N;
     vector<int> num;
     vector<char> op;
     dfs(, num, op, );
     for (set<string>::iterator it = res.begin(); it != res.end(); it++) {
         fout << *it << endl;
     }

     ;
 }