目录
1.定义
int father[N];
2.初始化
for(int i=1;i<N;i++){
father[i] = i;
}
3.查找
int findfather(int x){
while(x!=father[x]){
x=father[x];
}
return x;
}
int findfather(int x){
if(x==father[x]) return x;
else return findfather(father[x]);
}
4.合并
void union(int a,int b){
int faa=findfather(a);
int fab=findfather(b);
if(faa!==fab){
father[faa] = fab;
}
}
5.优化的查找
int findfather(int x){
int a= x;
while(x!=father[x]){
x=father[x];
}
while(a!=father[a]){
int z = a;
a=father[a];
father[z] = x;
}
return x;
}
int findfather(int v){
if(v==father[v]) return v;
else{
int f=findfather(father[v]);
father[v] = f;
return f;
}
}
6.好朋友
#include<cstdio>
#include<cmath>
#include<vector>
#include<queue>
#include<algorithm>
using namespace std;
const int N = 110;
int father[N];
bool isroot[N];
int findfather(int x){
int a= x;
while(x!=father[x]){
x=father[x];
}
while(a!=father[a]){
int z=a;
a=father[a];
father[z] = x;
}
return x;
}
void unions(int a,int b){
int faa=findfather(a);
int fbb=findfather(b);
if(faa!=fbb){
father[faa] = fbb;
}
}
void init(int n){
for(int i=1;i<=n;i++){
father[i] = i;
isroot[i] = false;
}
}
int main(){
int n,m,a,b;
scanf("%d",&n,&m);
init(n);
for(int i=0;i<m;i++){
scanf("%d%d",&a,&b);
unions(a,b);
}
for(int i=1;i<=n;i++){
isroot[findfather(i)]=true;
}
int ans=0;
for(int i=1;i<=n;i++){
ans+=isroot[i];
}
printf("%d\n",ans);
return 0;
}
7.Social Clusters
#include<cstdio>
#include<cmath>
#include<vector>
#include<queue>
#include<algorithm>
using namespace std;
const int N = 1010;
int father[N];
int isroot[N] = {0};
int course[N] = {0};
int findfather(int x){
int a = x;
while(x!=father[x]){
x = father[x];
}
while(a!=father[a]){
int z = a;
a=father[a];
father[z] = x;
}
return x;
}
void unions(int a,int b){
int faa=findfather(a);
int fab=findfather(b);
if(faa!=fab){
father[faa] = fab;
}
}
void init(int n){
for(int i=1;i<=n;i++){
father[i] = i;
isroot[i] = false;
}
}
bool cmp(int a,int b){
return a>b;
}
int main(){
int n;
scanf("%d",&n);
init(n);
int k,h;
for(int i=1;i<=n;i++){
scanf("%d:",&k);
for(int j=0;j<k;j++){
scanf("%d",&h);
if(course[h]==0){
course[h] = i;
}
unions(i,findfather(course[h]));
}
}
for(int i=1;i<=n;i++){
isroot[findfather(i)]++;
}
int ans=0;
for(int i=1;i<=n;i++){
if(isroot[i]!=0){
ans++;
}
}
printf("%d\n",ans);
sort(isroot+1,isroot+n+1,cmp);
for(int i=1;i<=ans;i++){
printf("%d",isroot[i]);
if(i<ans) printf(" ");
}
return 0;
}