2.3.3 Zero Sum

/*
ID: awsd1231
PROG: zerosum
LANG: C++
*/
#include<iostream>
#include<cstdio>
#include<string>
using namespace std;
int n;
char ch[] = {‘+‘, ‘-‘, ‘ ‘};
void dfs(int x, int change, int befVal, string tmpS) {
	char tc = x + ‘0‘;
	switch (change) {
		case 0 : tmpS += "+"; tmpS += tc; befVal += x; break;
		case 1 : tmpS += "-"; tmpS += tc; befVal -= x; break;
		case 2 : char tmp = ‘+‘; int tmpVal = 0;
				 for (int i = 0; i != tmpS.length(); ++i) {
					 if (tmpS[i] != ‘ ‘ && (tmpS[i] < ‘1‘ || tmpS[i] > ‘9‘)) {
						 tmp = tmpS[i];
						 tmpVal = 0;
					 }
					 else if (tmpS[i] != ‘ ‘) {
						 tmpVal = tmpVal * 10 + tmpS[i] - ‘0‘;
					 }
				 }
				 switch (tmp) {
					case ‘+‘ : befVal += tmpVal * 9 + x; break;
					case ‘-‘ : befVal -= tmpVal * 9 + x; break;
				 }
				 tmpS += " "; tmpS += tc; break;
	}
	if(x == n) {
		if (befVal == 0)
			cout << tmpS << endl;
		return;
	}
	dfs(x + 1, 2, befVal, tmpS);
	dfs(x + 1, 0, befVal, tmpS);
	dfs(x + 1, 1, befVal, tmpS);
}
int main () {
	freopen("zerosum.in", "r", stdin); 
	freopen("zerosum.out", "w", stdout);
	scanf("%d", &n);
	string ans("1");
	dfs(2, 2, 1, ans);
	dfs(2, 0, 1, ans);
	dfs(2, 1, 1, ans);
	return 0;		
}