Timus: Stone Pile (All possible Combination)

#include <bits/stdc++.h>
using namespace std;
#define d(x)                cout << #x << " = " << (x) << endl;
#define fr                  freopen("in.txt", "r", stdin);
#define fw                  freopen("out.txt", "w", stdout);
#define mem(x)              memset((x), 0, sizeof((x)));
#define pb                  push_back
#define LL                  long long
#define fastIO              ios_base::sync_with_stdio(false)
#define sf                  scanf
#define pf                  printf
#define SQR(x)              ((x)*(x))
#define sc1(x)              scanf("%d", &x)
#define sc2(x, y)           scanf("%d %d", &x, &y)
#define sc3(x, y, z)        scanf("%d %d %d", &x, &y, &z)
#define FOR(i, x, y)        for(int i=int(x); i<int(y); i++)
#define ROF(i, x, y)        for(int i=int(x-1); i>=int(y); i--)
#define all(c)              (c.begin(), c.end())
#define unq(v)              sort(all(v)), (v).erase(unique(all(v)),v.end())
#define siz 100000
#define EPSILON    (1.0E-8)

int n;
int whole_sum = 0;
int mini = INT_MAX;
int ara[siz];
int ans[siz];
int used[siz];

int bt(int pos, int j, int x){
    if(pos == x){
        int sum = 0;
        for(int i = 0; i < x; i++) sum += ans[i];
        int temp = abs((whole_sum-sum)-sum);
        if(temp < mini) mini = temp;
        // for(int i = 0; i < x; i++) cout << ans[i] << " ";
        // cout << endl;
        return 0;
    }
    for(int i = j; i < n; i++){
        if(used[i] == 0){
            used[i] = 1;
            ans[pos] = ara[i];
            bt(pos+1, i, x);
            used[i] = 0;
        }
    }
}

int main(){
    #ifndef ONLINE_JUDGE
        clock_t tStart = clock();
        freopen("in.txt", "r", stdin);
        freopen("out.txt", "w", stdout);
    #endif

        cin >> n;
        for(int i = 0; i < n; i++){
            cin >> ara[i];
            whole_sum += ara[i];
        }

        for(int i = 1; i <= n; i++){
            mem(ans);
            mem(used);
            bt(0, 0, i);
        }
        cout << mini << endl;


    #ifndef ONLINE_JUDGE
        printf("\n>>Time taken: %.10fs\n", (double) (clock() - tStart) / CLOCKS_PER_SEC);
    #endif
}