HDU_Virtual Friends (并查集)

　

　／＊贡献出无数WA， 就因为一个地方写错， 悲剧的一晚上啊！不过能过了还是很爽的。

　　思路：用Trie树给字符串重新标号，然后用并查集，用一个a[i] 记录当前并查集跟结点上连接的结点数。＊／



#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

struct node
{
    int flag;
    node * next[53];
};

const int N = 200005;

int parent[N];
int rank[N];
int a[N];
int num;

node * newnode()
{
    node *p = new node;
    p->flag = 0;
    for(int i = 0; i < 52; i++)
        p->next[i] = NULL;
    return p;
}

int insert(node *root, char *s)
{
    node *p = root;
    int i, len = strlen(s), t;
    for(i = 0; i < len; i++)
    {
        if(isupper(s[i]))
            t = s[i] - 'A';
        else
            t = s[i] - 'a' + 26;

        if(p->next[t] == NULL)
            p->next[t] = newnode();
        p = p->next[t];
    }
    if(p->flag)
        return p->flag;
    else
    {
        p->flag = num++;
        return p->flag;
    }
}

void del(node *p)
{
    if(p)
    {
        for(int i = 0; i < 52; i++)
            if(p->next[i])
                del(p->next[i]);
    }
    delete p;
    p = NULL;
}

void init()
{
    for(int i = 0; i < N; i++)
    {
        parent[i] = i;
        a[i] = 1;
    }
}
int find(int x)
{
    int k = x, r = x, j;
    while(r != parent[r])
        r = parent[r];
    while(k != r)
    {
        j = parent[k];
        parent[k] = r;
        k = j;
    }
    return r;
}

void union_set(int x, int y)
{
    x = find(x);
    y = find(y);

    if(x == y)    return ;

    parent[x] = y;
    a[y] += a[x];
}

int main()
{
    //freopen("data.in", "r", stdin);

    int t, n, x, y;
    char s1[35], s2[35];

    node * root;

    while(scanf("%d", &t) != EOF)
    {
        while(t--)
        {
            scanf("%d", &n);

            if(n == 0)
            {
                printf("0\n");
                continue;
            }

            init(); num = 1;
            root = newnode();

            while(n--)
            {
                scanf("%s%s", s1, s2);

                x = insert(root, s1);
                y = insert(root, s2);

                union_set(x, y);
                printf("%d\n", a[find(y)]);   //一直写成a[y],贡献出无数WA！！！

            }
            del(root);
        }
    }
    return 0;
}