寻找和为定值的递归算法

//寻找和为定值的多个数：
#include<iostream>
#include<list>
using namespace std;


list<int> ecv;


void sumofnum(int sum, int num)
{
//递归出口：
if (num <= 0 || sum <= 0)
{
return;
}
if (sum == num)
{
ecv.reverse();
//list<int>::iterator it = ecv.begin();
for (list<int>::iterator it = ecv.begin(); it != ecv.end(); ++it)
cout << *it << "+";

cout << num << endl;
ecv.reverse();
}


ecv.push_front(num);
sumofnum(sum - num, num - 1);//放num；
ecv.pop_front();
sumofnum(sum, num - 1);//不放num
}


//测试函数：
int main()
{
//int s[] = { 12, 45, 78, 63, 21, 32, 30, 87, 89 };
int sum;
int n;
cout << "请输入你要等于多少的数值sum:" << endl;
cin >> sum;
cout << "请输入你要从1.....n数列中取值的n：" << endl;
cin >> n;
sumofnum(sum, n);
return 0;
}