BZOJ 1202 狡猾的商人(带权并查集)

时间：2023-03-09 15:50:01
BZOJ 1202 狡猾的商人(带权并查集)

给出了l,r,w。我们就得知了s[r]-s[l-1]=w.也就是说，点l-1和点r的距离为w。

于是可以使用带权并查集，定义dis[i]表示点i到根节点的距离。查询和合并的时候维护一下就OK了。

如果账本有错误，那么这两点的距离一定不等于在并查集上面的距离。

# include <cstdio>

# include <cstring>

# include <cstdlib>

# include <iostream>

# include <vector>

# include <queue>

# include <stack>

# include <map>

# include <set>

# include <cmath>

# include <algorithm>

using namespace std;

# define lowbit(x) ((x)&(-x))

# define pi acos(-1.0)

# define eps 1e-

# define MOD

# define INF

# define mem(a,b) memset(a,b,sizeof(a))

# define FOR(i,a,n) for(int i=a; i<=n; ++i)

# define FO(i,a,n) for(int i=a; i<n; ++i)

# define bug puts("H");

# define lch p<<,l,mid

# define rch p<<|,mid+,r

# define mp make_pair

# define pb push_back

typedef pair<int,int> PII;

typedef vector<int> VI;

# pragma comment(linker, "/STACK:1024000000,1024000000")

typedef long long LL;

int Scan() {

    int res=, flag=;

    char ch;

    if((ch=getchar())=='-') flag=;

    else if(ch>=''&&ch<='') res=ch-'';

    while((ch=getchar())>=''&&ch<='')  res=res*+(ch-'');

    return flag?-res:res;

}

void Out(int a) {

    if(a<) {putchar('-'); a=-a;}

    if(a>=) Out(a/);

    putchar(a%+'');

}

const int N=;

//Code begin...

int fa[], dis[];

int find(int x)

{

    int tmp;

    if (fa[x]!=x) {

        tmp=find(fa[x]);

        dis[x]+=dis[fa[x]];

        fa[x]=tmp;

    }

    return fa[x];

}

int main ()

{

    int n, m, T, l, r, w;

    scanf("%d",&T);

    while (T--) {

        mem(dis,);

        int flag=;

        scanf("%d%d",&n,&m);

        FOR(i,,n) fa[i]=i;

        while (m--) {

            scanf("%d%d%d",&l,&r,&w);

            if (!flag) continue;

            int u=find(l-), v=find(r);

            if (u!=v) {

                dis[u]=dis[r]+w-dis[l-];

                fa[u]=v;

            }

            else {

                if (dis[l-]-dis[r]!=w) flag=;

            }

        }

        puts(flag?"true":"false");

    }

    return ;

}

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