Luogu2798 爆弹虐场（二分，Kruskal）

二分答案，判定连通性

#include <iostream>

#include <cstdio>

#include <cstring>

#include <algorithm>

#include <cmath>

#define R(a,b,c) for(register int  a = (b); a <= (c); ++ a)

#define nR(a,b,c) for(register int  a = (b); a >= (c); -- a)

#define Max(a,b) ((a) > (b) ? (a) : (b))

#define Min(a,b) ((a) < (b) ? (a) : (b))

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

#define Abs(a) ((a) < 0 ? -(a) : (a))

#define Swap(a,b) a^=b^=a^=b

#define ll long long

#define ON_DEBUG

#ifdef ON_DEBUG

#define D_e_Line printf("\n\n----------\n\n")

#define D_e(x)  cout << #x << " = " << x << endl

#define Pause() system("pause")

#define FileOpen() freopen("in.txt","r",stdin);

#else

#define D_e_Line ;

#define D_e(x)  ;

#define Pause() ;

#define FileOpen() ;

#endif

struct ios{

    template<typename ATP>ios& operator >> (ATP &x){

        x = 0; int f = 1; char c;

        for(c = getchar(); c < '0' || c > '9'; c = getchar()) if(c == '-')  f = -1;

        while(c >= '0' && c <= '9') x = x * 10 + (c ^ '0'), c = getchar();

        x*= f;

        return *this;

    }

}io;

using namespace std;

const int N = 20007;

int n, k, m;

struct Node{

    int x, y, w1, w2;

}a[N];

inline bool cmp_w1(const Node &a, const Node &b){

	return a.w1 < b.w1;

}

inline bool cmp_w2(const Node &a, const Node &b){

	return a.w2 < b.w2;

}

int fa[N];

inline int Find(int x){

	return x == fa[x] ? x : fa[x] = Find(fa[x]);

}

inline bool Check(int tim){

    int totTeen = 0, totLeason = 0;

    R(i,1,n) fa[i] = i;

    R(i,1,m){

    	int p = Find(a[i].x), q = Find(a[i].y);

    	if(p != q && tim >= a[i].w2){

    		if(a[i].w1 <= tim) ++totTeen;

    		fa[p] = q;

    		++totLeason;

    	}

    }

    return ((totLeason >= n - 1) && (totTeen >= k));

}

int main(){

	io >> n >> k >> m;

    R(i,1,m){

    	io >> a[i].x >> a[i].y >> a[i].w1 >> a[i].w2;

    }

    sort(a + 1, a + m + 1, cmp_w1);

    int l = 1, r = 1e6;

    while(l <= r){

    	int mid = (l + r) >> 1;

    	if(Check(mid))

    		r = mid - 1;

    	else

    		l = mid + 1;

    }

    printf("%d", l);

    return 0;

}

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Luogu2798 爆弹虐场（二分，Kruskal）

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Luogu2798 爆弹虐场（二分，Kruskal）