UVa 574 - Sum It Up, https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=515

uva-574.cpp

#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <vector>
#include <list>
#include <algorithm>
#include <string.h>

#define MAX 1000

int m[MAX];
using namespace std;

list<int> lst;
vector< vector<int> > result;

int t = 0, n = 0;
bool found = false;

void find(int pos, int sub_t) {
	if(t == sub_t) {
		for(int i=0; i<result.size(); i++) {
			if(result[i].size() != lst.size()) continue;
			
			bool eq = true;
			int idx = 0;
			for(list<int>::reverse_iterator p = lst.rbegin(); eq && p != lst.rend(); p++) {
				eq = result[i][idx++] == m[*p];
			}
			
			if(eq) return;
		}
		
		vector<int> v;
		for(list<int>::reverse_iterator p = lst.rbegin(); p != lst.rend(); p++) {
			if(p != lst.rbegin()) printf("+");			
			printf("%d", m[*p]);
			v.push_back(m[*p]);
			
			found = true;	
		}
		
		result.push_back(v);
		
		printf("\n");
		return;
	}
	
	for(int i=0; i<n; i++) {
		if(i > pos) {
			lst.push_front(i);		
			find(i, m[i] + sub_t);
			lst.pop_front();
		}
	}
}

int main(void) {
	scanf("%d %d", &t, &n);
	while (n != 0) {
        for(int i=0; i<n; i++) {
            scanf("%d", &m[i]);
        }

		lst.clear();
		result.clear();
		
		found = false;
		
        printf("Sums of %d:\n", t);
		find(-1, 0);
		if(!found) printf("NONE\n", t);

    	scanf("%d %d", &t, &n);
	}
	return EXIT_SUCCESS;
}