Day3-E-New Year Snowmen CodeForces140C

As meticulous Gerald sets the table and caring Alexander sends the postcards, Sergey makes snowmen. Each showman should consist of three snowballs: a big one, a medium one and a small one. Sergey's twins help him: they've already made n snowballs with radii equal to r₁, r₂, ..., r_n. To make a snowman, one needs any three snowballs whose radii are pairwise different. For example, the balls with radii 1, 2 and 3 can be used to make a snowman but 2, 2, 3 or 2, 2, 2 cannot. Help Sergey and his twins to determine what maximum number of snowmen they can make from those snowballs.

Input

The first line contains integer n (1 ≤ n ≤ 10⁵) — the number of snowballs. The next line contains n integers — the balls' radii r₁, r₂, ..., r_n (1 ≤ r_i ≤ 10⁹). The balls' radii can coincide.

Output

Print on the first line a single number k — the maximum number of the snowmen. Next k lines should contain the snowmen's descriptions. The description of each snowman should consist of three space-separated numbers — the big ball's radius, the medium ball's radius and the small ball's radius. It is allowed to print the snowmen in any order. If there are several solutions, print any of them.

Examples

Input

7
1 2 3 4 5 6 7

Output

2
3 2 1
6 5 4

Input

3
2 2 3

Output

0

思路：贪心，每次选出还剩的最大的三个组成一个雪人，用优先队列为数据结构，代码如下：

struct Node {

    int id, sum;

    Node(int _id = , int _sum = ) : id(_id), sum(_sum){}

    bool operator<(const Node &a) const {

        return sum < a.sum;

    }

};

struct Snowman {

    int a, b, c;

    Snowman(int _a, int _b, int _c) : a(_a), b(_b), c(_c){}

};

bool comp(int a,int b) {

    return a > b;

}

map<int, int> Cache;

vector<Snowman> res;

int n;

int main() {

    scanf("%d", &n);

    priority_queue<Node> q;

    for (int i = ; i < n; ++i) {

        int tmp;

        scanf("%d", &tmp);

        Cache[tmp]++;

    }

    for(auto i = Cache.begin(); i != Cache.end(); ++i)

        q.push(Node(i->first,i->second));

    while(q.size() > ) {

        Node t1, t2, t3;

        t1 = q.top(), q.pop();

        t2 = q.top(), q.pop();

        t3 = q.top(), q.pop();

        res.push_back(Snowman(t1.id, t2.id, t3.id));

        t1.sum--, t2.sum--, t3.sum--;

        if(t1.sum > ) q.push(t1);

        if(t2.sum > ) q.push(t2);

        if(t3.sum > ) q.push(t3);

    }

    printf("%d\n", res.size());

    for (int i = ; i < res.size(); ++i) {

        int tmp[];

        tmp[] = res[i].a, tmp[] = res[i].b, tmp[] = res[i].c;

        sort(tmp, tmp + , comp);

        for(int j = ; j < ; ++j) {

            if(j)

                printf(" ");

            printf("%d", tmp[j]);

        }

        printf("\n");

    }

    return ;

}

巴特西

Day3-E-New Year Snowmen CodeForces140C

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