一种使用进制生成全排列的方法。

permutation

#include <iostream>
#include <cassert>
#include <cmath>

using namespace std;

char a[3] = { '+', '+', '+' };

int i = 0;	
const int base = 4; /* [+,-,*,/] */
bool next() {
	i++;
	if (i >= (int)pow((double)base, 3)) {
		return false;
	}

	int x = i;

	for (int j = 0; j < 4; j++) {
		int value = x % base;
		x /= base;
		switch (value) {
			case 0:
				a[j] = '+';
				break;
			case 1:
				a[j] = '-';
				break;
			case 2:
				a[j] = '*';
				break;
			case 3:
				a[j] = '/';
				break;
			default:
				return false;
		}
	}
	return true;
}

int main(int argc, char* argv[]) {
	do {
		cout << a[0] << a[1] << a[2] << endl;
	}
	while (next());
	return 0;
}