C++ 解法, 执行用时: 1ms, 内存消耗: 220KB, 提交时间: 2017-06-11

#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
using namespace std;
void dfs(vector<int>& curp, vector<vector<int>>& rst, int curn, int n, int tar){
	if (tar == 0){
		rst.push_back(curp);
	}
	for (int i = curn; i <= n; i++){
		curp.push_back(i);
		dfs(curp, rst, i + 1, n, tar - i);
		curp.pop_back();
	}
}
int main(){
	int n, m; cin >> n >> m;
	vector<int> curp;
	vector<vector<int>> rst;
	dfs(curp, rst, 1,n, m);
	for (int i = 0; i < rst.size(); i++){
		cout << rst[i][0];
		for (int j = 1; j < rst[i].size(); j++){
			cout << " "<<rst[i][j];
		}
		cout << endl;
	}
	return 0;
}

C++ 解法, 执行用时: 1ms, 内存消耗: 364KB, 提交时间: 2017-09-03

#include<iostream>
#include<vector>
using namespace std;
void helper(vector<int>& num, int begin, int n, int m)
{
	if (m == 0)
	{
		for (int i = 0; i < num.size(); i++)
		{
			i == 0 ? cout << num[i] : cout << " " << num[i];
		}
		cout << endl;
	}
	for (int i = begin; i <= n&&i <= m; i++)
	{
		num.push_back(i);
		helper(num, i + 1, n, m - i);
		num.pop_back();
	}
}

int main()
{
	int n, m;
	while (cin >> n >> m)
	{
		vector<int> num;
		helper(num, 1, n, m);
	}
	return 0;
}