kuangbin专题五：并查集

  不想写实验，不想改paper，写点代码吧（；´д｀）ゞ

 

POJ2236 Wireless Network

思路：简单并查集。

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
const int INF = 0x3f3f3f3f;
const int maxn = 1e3 + 5;
int N, D;
int p[maxn];
bool vis[maxn];

struct Pos{
    int x, y;
}pos[maxn];

int findP(int x){
    return x == p[x] ? x : p[x] = findP(p[x]);
}

void Union(int x, int y){
    int px = findP(x), py = findP(y);
    if(px != py)
        p[px] = py;
}

bool in_dis(int x, int y){
    int dx = pos[x].x - pos[y].x;
    int dy = pos[x].y - pos[y].y;
    return dx*dx + dy*dy <= D*D;
}

void repair(int x){
    for(int i = 1; i <= N; i++)
        if(vis[i] && in_dis(i, x))
            Union(i, x);
    vis[x] = true;
}

int main(){
    cin >> N >> D;

    for(int i = 1; i <= N; i++) p[i] = i;

    for(int i = 1; i <= N; i++)
        cin >> pos[i].x >> pos[i].y;

    char op;
    int u, v;
    while(cin >> op){
        if(op == 'O'){
            cin >> u;
            repair(u);
        }
        else{
            cin >> u >> v;
            int pu = findP(u), pv = findP(v);
            cout << (pu == pv ? "SUCCESS" : "FAIL") << endl;
        }
    }
    return 0;
}

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POJ1611 The Suspects

思路：简单并查集。

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
const int INF = 0x3f3f3f3f;
const int maxn = 3e4 + 5;
const int maxm = 505;
int p[maxn];

inline int findP(int x){
    return x == p[x] ? x : p[x] = findP(p[x]);
}

inline void Union(int x, int y){
    int px = findP(x), py = findP(y);
    if(px != py)
        p[px] = py;
}

int main(){
    int n, m;
    while(cin >> n >> m && (n + m > 0)){
        for(int i = 0; i < n; i++) p[i] = i;

        int k, s1, s2;
        for(int i = 1; i <= m; i++){
            cin >> k;
            if(k) cin >> s1;
            for(int j = 1; j < k; j++){
                cin >> s2;
                Union(s1, s2);
            }
        }
        int res = 0;
        for(int i = 0; i < n; i++)
            if(findP(0) == findP(i))
                res++;
        cout << res << endl;
    }
    return 0;
}

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HDU1213 How Many Tables

思路：简单并查集。

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
const int INF = 0x3f3f3f3f;
const int maxn = 1e3 + 5;
const int maxm = 1e3 + 5;
int p[maxn];
bool vis[maxn];

inline int findP(int x){
    return x == p[x] ? x : p[x] = findP(p[x]);
}

inline void Union(int x, int y){
    int px = findP(x), py = findP(y);
    if(px != py)
        p[px] = py;
}

int main(){
    int T;
    cin >> T;
    while(T--){
        int n, m;
        cin >> n >> m;

        for(int i = 1; i <= n; i++) p[i] = i;
        memset(vis, 0, sizeof(vis));

        for(int i = 1; i <= m; i++){
            int x, y;
            cin >> x >> y;
            Union(x, y);
        }

        int res = 0;
        for(int i = 1; i <= n; i++){
            int pi = findP(i);
            if(!vis[pi]){
                vis[pi] = true;
                res++;
            }
        }
        cout << res << endl;
    }
    return 0;
}

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HDU3038 How Many Answers Are Wrong

思路：带权并查集。这题个人觉得模型比较难想到，我第一次接触到的时候被提醒了才想起来带权并查集。

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
const int maxn = 2e5 + 5;
int p[maxn], w[maxn];

int findP(int x){
    if(x != p[x]){
        int px = p[x];
        p[x] = findP(p[x]);
        w[x] += w[px];
    }
    return p[x];
}

int main(){
    int n, m;
    while(scanf("%d%d", &n, &m) != EOF){
        for(int i = 0; i <= n; i++) p[i] = i, w[i] = 0;

        int res = 0;
        while(m--){
            int a, b, s;
            scanf("%d%d%d", &a, &b, &s);
            a--;
            int pa = findP(a), pb = findP(b);
            if(pa == pb){
                if((w[a] - w[b]) != s) res++;
            }
            else{
                p[pa] = pb;
                w[pa] = w[b] - w[a] + s;
            }
        }
        cout << res << endl;
    }
    return 0;
}

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POJ1182 食物链

思路：经典带权并查集问题了。

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
const int maxn = 5e4 + 5;
int p[maxn], w[maxn];

int findP(int x){
    if(x != p[x]){
        int px = p[x];
        p[x] = findP(p[x]);
        w[x] = (w[x] + w[px]) % 3;
    }
    return p[x];
}

int main(){
    int n, m;
    scanf("%d%d", &n, &m);
    for(int i = 1; i <= n; i++) p[i] = i, w[i] = 0;

    int res = 0;
    while(m--){
        int d, x, y;
        scanf("%d%d%d", &d, &x, &y);

        if (x > n || y > n) {
            res++;
            continue;
        }
        if (d == 2 && x == y) {
            res++;
            continue;
        }
        d--;

        int px = findP(x), py = findP(y);
        if (px == py && (w[y] - w[x] + 3) % 3 != d){
            res++;
        }
        else {
            p[py] = px;
            w[py] = (w[x] + d - w[y] + 3) % 3;
        }
    }
    cout << res << endl;
    return 0;
}

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POJ1417 True Liars

思路：

 

标签：专题,int,px,查集,maxn,kuangbin,py,include,findP
来源： https://www.cnblogs.com/arch/p/14352743.html