并查集

并查集模板

包含路径压缩+小挂大

const int MAXN = 1e5 + 1;
int father[MAXN];  // 存父亲节点 father[1] =2 指的是1节点的父亲为2
int size[MAXN];	   // 存每个集合的大小
int stack[MAXN];   // 
int n;

// 建立并查集
void build(){
	for(int i = 0; i <= n; i ++ ){
        father[i] = i;
        size[i] = 1;
    }
}

// 查找元素
int find(int i){
    // 沿途收集了几个点
	int size = 0;
    while(i != father[i]){
        stack[size ++ ] = i;
        i = father[i];
    }
    // 沿途节点收集好了，i已经跳到代表节点了
    while(size > 0){
        father[stack[-- size ]] = i;
    }
    return i;
}

bool isSameSet(int x, int y){
    return find(x) == find(y);
}

void union(int x, int y){
    int fx = find(x);
    int fy = find(y);
    if(fx != fy){
        if(size[fx] >= size[fy]){
            size[fx] += size[fy];
            father[fy] = fx;
        }else{
            size[fy] += size[fx];
            father[fx] = fy;
        }
    }
}

并查集模板（精简版）

路径压缩

const int MAXN = 1001;
int father[MANX];
int n;

void build(){
    for(int i = 0; i <= n; i ++ ){
        father[i] = i;
    }
}

int find(int i){
    if(i != father[i]){
        father[i] = find(father[i]);  // 路径压缩
    }
	return father[i];
}

bool isSameSet(int x, int y){
    return find(x) == find(y);
}

void union(int x, int y){
    father[find(x)] = find(y);
}