UASCO Zero Sum DFS + Stack

给一个N 表示1 2 3 ...N

求出所有 zero sum的情况

【简单Dfs 即可】 运算结果的时候我使用了一个stack...

比如N = 7

那么要求输出

1+2-3+4-5-6+7
1+2-3-4+5+6-7
1-2 3+4+5+6+7
1-2 3-4 5+6 7
1-2+3+4-5+6-7
1-2-3-4-5+6+7

Source Code:

/*
ID: wushuai2
PROG: zerosum
LANG: C++
*/
//#pragma comment(linker, "/STACK:16777216") //for c++ Compiler
#include <stdio.h>
#include <iostream>
#include <fstream>
#include <cstring>
#include <cmath>
#include <stack>
#include <string>
#include <map>
#include <set>
#include <list>
#include <queue>
#include <vector>
#include <algorithm>
#define Max(a,b) (((a) > (b)) ? (a) : (b))
#define Min(a,b) (((a) < (b)) ? (a) : (b))
#define Abs(x) (((x) > 0) ? (x) : (-(x)))
#define MOD 1000000007
#define pi acos(-1.0)
#define RV(num) ((num) > 0 ? 0 : 1)

using namespace std;

typedef long long           ll      ;
typedef unsigned long long  ull     ;
typedef unsigned int        uint    ;
typedef unsigned char       uchar   ;

template<class T> inline void checkmin(T &a,T b){if(a>b) a=b;}
template<class T> inline void checkmax(T &a,T b){if(a<b) a=b;}

const double eps = 1e-7      ;
const int M = 660000         ;
const ll P = 10000000097ll   ;
const int INF = 0x3f3f3f3f   ;
const int MAX_N = 20         ;
const int MAXSIZE = 101000000;

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

int N, b[11];
void solve(){
    int i, j, t;
    vector <int> vec;
    vec.push_back(1);
    for(i = 2; i <= N; ++i){
        int num = vec[vec.size() - 1];
        if(num < 0){
            num = vec[vec.size() - 2];
        }
        if(b[i] == 1){
            vec.pop_back();
            vec.push_back(num * 10 + i);
        } else if(b[i] == 2){
            vec.push_back(-1);
            vec.push_back(i);
        } else if(b[i] == 3){
            vec.push_back(-2);
            vec.push_back(i);
        } else{
            vec.push_back(i);
        }
    }

    int ans = vec[0];
    for(i = 1; i < vec.size(); i += 2){
        if(vec[i] == -1){
            ans += vec[i + 1];
        } else if(vec[i] == -2){
            ans -= vec[i + 1];
        }
    }
    if(ans == 0){
        fout << 1;
        for(i = 2; i <= N; ++i){
            if(b[i] == 1)   fout << ‘ ‘;
            else if(b[i] == 2)  fout << ‘+‘;
            else if(b[i] == 3)  fout << ‘-‘;
            fout << i;
        }
        fout << endl;
    }
}

void change(int n){
    int i, j;
    if(n == N + 1){
        solve();
        return;
    }
    for(i = 1; i <= 3; ++i){
        b[n] = i;
        change(n + 1);
    }
}

int main() {
    int i, j, k, l, m, n, t, s, c, w, q, num;
    fin >> N;
    for(i = 2; i <= N; ++i){
        b[i] = 1;
    }
    change(2);

    fin.close();
    fout.close();
    return 0;
}