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SumCalc.cpp

// Input: N, Y ---> Output Several Numbers' Sum == Y
#include <vector>
#include <iostream>
#include <algorithm>
#include <functional>
#include <cstring>
#include <cstdlib>

using namespace std;

const int MAX_NUMBER = 100;
const int MAX_SUM = 100;

using Index = unsigned int;
Index f[MAX_NUMBER][MAX_SUM];
vector<int> NList[MAX_NUMBER*MAX_SUM];
int NSum[MAX_NUMBER*MAX_SUM];
int ListUsed;
int s[MAX_NUMBER];
int N, Y;

int GetIndex(Index& Pos)
{
	if (Pos != 0)return Pos;
	Pos = ListUsed;
	NSum[ListUsed] = 0;
	ListUsed++;
	return Pos;
}

vector<int>Path;
void PrintPath(int i, int Y)
{
	if (Y - s[i] == 0)
	{
		for (const auto p : Path)
		{
			cout << s[p] << " ";
		}
		cout << endl;
		return;
	}
	if (Y < 0)return;
	int __index = GetIndex(f[i][Y]);
	for (const auto p : NList[__index])
	{
		Path.push_back(p);
		PrintPath(p, Y - s[i]);
		Path.pop_back();
	}
}

int main()
{
	cin >> N >> Y;
	ListUsed = 1;
	for (int i = 0; i < N; i++)cin >> s[i];
	memset(f, sizeof(f), 0);
	int __index = GetIndex(f[0][s[0]]);
	NSum[__index] = 1;
	for (int i = 1; i < N; i++)
	{
		int __Index = GetIndex(f[i][s[i]]);
		NSum[__Index] = 1;
		for (int j = 0; j < i; j++)
		{
			for (int k = 1; k <= Y; k++)
			{
				int __PrevIndex = GetIndex(f[j][k]);
				if (NSum[__PrevIndex] <= 0)continue;
				int __CurIndex = GetIndex(f[i][k + s[i]]);
				
				NSum[__CurIndex] += NSum[__PrevIndex];
				NList[__CurIndex].push_back(j);
			}
		}
	}
	int ans = 0;
	for (int i = 0; i < N; i++)
	{
		int __index = GetIndex(f[i][Y]);
		Path.push_back(i);
		if (NSum[__index] != 0)
		{
			ans += NSum[__index];
			PrintPath(i, Y);
		}
		Path.pop_back();
	}
	cout << ans << endl;
	system("PAUSE");
	return 0;
}

This programm for Windows?