Usaco zerosum DFS 1A

USER: Kevin Samuel [kevin_s1]TASK: zerosumLANG: C++Compiling...Compile: OKExecuting...   Test 1: TEST OK [0.003 secs, 3508 KB]   Test 2: TEST OK [0.003 secs, 3508 KB]   Test 3: TEST OK [0.005 secs, 3508 KB]   Test 4: TEST OK [0.000 secs, 3508 KB]   Test 5: TEST OK [0.005 secs, 3508 KB]   Test 6: TEST OK [0.008 secs, 3508 KB]   Test 7: TEST OK [0.014 secs, 3508 KB]All tests OK.
YOUR PROGRAM (‘zerosum‘) WORKED FIRST TIME!  That‘s fantastic-- and a rare thing.  Please accept these special automatedcongratulations.

Here are the test data inputs:

------- test 1 ----3------- test 2 ----4------- test 3 ----5------- test 4 ----6------- test 5 ----7------- test 6 ----8------- test 7 ----9

Keep up the good work!

Thanks for your submission!

It's a easy problem of DFS

/*ID:kevin_s1PROG:zerosumLANG:C++*/#include <iostream>#include <cstdio>#include <string>#include <cstring>#include <vector>#include <map>#include <set>#include <algorithm>#include <cstdlib>#include <list>#include <cmath>using namespace std;//gobal variable====int N;vector<string> result;//==================//function==========char NumToChar(int i){char ch = i + 48;return ch;}void DFS(int i, int sum, string str, int last_operator){if(i > N + 1)return;if(i == N + 1){if(sum == 0){result.push_back(str);}return;}//plusstring tmp1 = str;tmp1 = tmp1 + "+" + NumToChar(i);DFS(i + 1, sum + i, tmp1, i);//minusstring tmp2 = str;tmp2 = tmp2 + "-" + NumToChar(i); DFS(i + 1, sum - i, tmp2, -i);//multiplystring tmp3 = str;tmp3 = tmp3 + " " + NumToChar(i);int cc = 0;if(last_operator > 0)cc = 1;elsecc = -1;int mt = cc * (abs(last_operator) * 10 + i);int sum_tmp = sum - last_operator + mt;DFS(i + 1, sum_tmp, tmp3, mt);return;}//==================int main(){freopen("zerosum.in","r",stdin);freopen("zerosum.out","w",stdout);cin>>N;string str = "1";DFS(2, 1, str, 1);sort(result.begin(), result.end(), less<string>());vector<string>::iterator iter;for(iter = result.begin(); iter != result.end(); iter++){cout<<*iter<<endl;}return 0;}