POJ 1182 食物链

题意：就是……食物链嘛orz

解法：并查集+向量偏移。一！定！不！要！多！组！输！入！！！

偏移量0表示同类，1表示吃，2表示被吃

代码：

#include<stdio.h>
#include<iostream>
#include<algorithm>
#include<string>
#include<string.h>
#include<math.h>
#include<limits.h>
#include<time.h>
#include<stdlib.h>
#include<map>
#include<queue>
#include<set>
#include<stack>
#include<vector>
#define LL long long
using namespace std;
int father[50005], delta[50005];
void init()
{
    for(int i = 0; i < 50005; i++)
        father[i] = i;
    memset(delta, 0, sizeof delta);
}
int Find(int a)
{
    if(father[a] != a)
    {
        int tmp = Find(father[a]);
        delta[a] = (delta[a] + delta[father[a]]) % 3;
        father[a] = tmp;
    }
    return father[a];
}
int main()
{
    int n, k;
    scanf("%d%d", &n, &k);
        init();
        int ans = 0;
        for(int i = 0; i < k; i++)
        {
            int a, b, c;
            scanf("%d%d%d", &a, &b, &c);
            if(b > n || c > n)
            {
                ans++;
                continue;
            }
            int d, e;
            d = Find(b), e = Find(c);
            if(a == 1)
            {
                if(d == e)
                {
                    if(delta[b] != delta[c])
                        ans++;
                }
                else
                {
                    father[d] = e;
                    delta[d] = (delta[c] - delta[b] + 3) % 3;
                }
            }
            else
            {
                if(d == e)
                {
                    if(((delta[b] - delta[c] + 3) % 3) != 1)
                        ans++;
                }
                else
                {
                    father[d] = e;
                    delta[d] = (delta[c] - delta[b] + 4) % 3;
                }
            }
        }
        printf("%d
", ans);
    return 0;
}