UVA 1160 X-Plosives

题意是一次装入物品，物品由两种元素组成，当遇到即将装入的物品与已经装入的物品形成k个物品，k种元素，跳过该物品的装入。可以将每种元素看成顶点，物品看成一条边。这样问题就转化为利用并查集求环的情况。

算法竞赛训练指南中的代码：

 #include <iostream>
 #include <cstdio>
 #include <climits>
 #include <cstring>
 #include <cstdlib>
 #include <cmath>
 #include <vector>
 #include <queue>
 #include <algorithm>
 #define esp 1e-6
 #define pb push_back
 #define in  freopen("in.txt", "r", stdin);
 #define out freopen("out.txt", "w", stdout);
 #define print(a) printf("%d\n",(a));
 #define bug puts("********))))))");
 #define Rep(i, c) for(__typeof(c.end()) i = c.begin(); i != c.end(); i++)
 #define inf 0x0f0f0f0f
 using namespace std;
 typedef long long  LL;
 typedef vector<int> VI;
 typedef pair<int, int> pii;
 typedef vector<pii,int> VII;
 typedef vector<int>:: iterator IT;

 #define N (int)(1e5+100)
 int pa[N], rank[N];
 void init(void)
 {
     for(int i = ; i < N; i++)
         pa[i] = i;
     memset(rank, , sizeof(rank));
 }
 void merge(int x, int y)
 {
     if(rank[x] > rank[y])
         pa[y] = x;
     else {
         pa[x] = y;
         if(rank[x] == rank[y])
             rank[y]++;
     }
 }
 int findset(int x)
 {
     return  (pa[x] == x) ? x: pa[x] = findset(pa[x]);
 }
 int main(void)
 {
 int x, y;
     while(~scanf("%d", &x))
     {
         int cnt = ;
         init();
         while(x != -)
         {
             scanf("%d", &y);
             x = findset(x), y = findset(y);
             if(x == y)
                 cnt++;
                 else merge(x, y);
             scanf("%d", &x);
         }
         printf("%d\n", cnt);
     }
     return ;
 }