目录
1.深度优先搜索
1.1邻接矩阵
const int maxv = 1000;
const int inf = 100000000;
int n,g[maxv][maxv];
bool vis[maxv] = {false};
void dfs(int u,int depth){
vis[u] = true;
for(int v=0;v<n;v++){
if(vis[v]==false&&g[u][v]!=inf){
dfs(v,depth+1);
}
}
}
void dfstrave(){
for(int u=0;u<n;u++){
if(vis[u]==false){
dfs(u,1);
}
}
}2.2邻接表
const int maxv = 1000;
const int inf = 100000000;
vector<int> adj[maxv];
int n;
bool vis[maxv] = {false};
void dfs(int u,int depth){
vis[u] = true;
for(int i=0;i<adj[u].size();i++){
int v = adj[u][i];
if(vis[v]==false){
dfs(v,depth+1);
}
}
}
void dfstrave(){
for(int u=0;u<n;u++){
if(vis[u]==false){
dfs(u,1);
}
}
}2.3 Head of a Gang
#include<cstdio>
#include<cmath>
#include<vector>
#include<map>
#include<string>
#include<queue>
#include<algorithm>
#include<iostream>
using namespace std;
const int maxn = 2010;
const int inf = 100000000;
map<int,string> inttostring;
map<string,int> stringtoint;
map<string,int> gang;
int g[maxn][maxn] = {0},weight[maxn] = {0};
int n,k,numperson;
bool vis[maxn] = {false};
void dfs(int nowvisit,int& head,int& nummember,int& totalvalue){
nummember++;
vis[nowvisit] = true;
if(weight[nowvisit]>weight[head]){
head = nowvisit;
}
for(int i=0;i<numperson;i++){
if(g[nowvisit][i]>0){
totalvalue += g[nowvisit][i];
g[nowvisit][i]=g[i][nowvisit]=0;
if(vis[i]==false){
dfs(i,head,nummember,totalvalue);
}
}
}
}
void dfstrave(){
for(int i=0;i<numperson;i++){
if(vis[i]==false){
int head = i,nummember=0,totalvalue=0;
dfs(i,head,nummember,totalvalue);
if(nummember>2&&totalvalue>k){
gang[inttostring[head]] = nummember;
}
}
}
}
int change(string str){
if(stringtoint.find(str)!=stringtoint.end()){
return stringtoint[str];
}else{
stringtoint[str] = numperson;
inttostring[numperson] = str;
return numperson++;
}
}
int main(){
int w;
string str1,str2;
cin>>n>>k;
for(int i=0;i<n;i++){
cin>>str1>>str2>>w;
int id1=change(str1);
int id2=change(str2);
weight[id1]+=w;
weight[id2]+=w;
g[id1][id2]+=w;
g[id2][id1]+=w;
}
dfstrave();
cout<<gang.size()<<endl;
map<string,int>::iterator it;
for(it=gang.begin();it!=gang.end();it++){
cout<<it->first<<" "<<it->second<<endl;
}
return 0;
}2.广度优先搜索
2.1邻接矩阵
const int maxn = 2010;
const int inf = 100000000;
int n,g[maxn][maxn];
bool inq[maxn] = {false};
void bfs(int u){
queue<int> q;
q.push(u);
inq[u] = true;
while(!q.empty()){
int u = q.front();
q.pop();
for(int v=0;v<n;v++){
if(inq[v]==false&&g[u][v]!=inf){
q.push(v);
inq[v] = true;
}
}
}
}
void bfstrave(){
for(int u=0;u<n;u++){
if(inq[u]==false){
bfs(q);
}
}
}2.2邻接表
const int maxn = 2010;
const int inf = 100000000;
vector<int> adj[maxn];
int n;
bool inq[maxn] = {false};
void bfs(int u){
queue<int> q;
q.push(u);
inq[u] = true;
while(!q.empty()){
int u=q.front();
q.pop();
for(int i=0;i<adj[u].size();i++){
int v = adj[u][i];
if(inq[v]==false){
q.push(v);
inq[v] = true;
}
}
}
}
void bfstrave(){
for(int u=0;u<n;u++){
if(inq[u]==false){
bfs(q);
}
}
}2.3层号版
const int maxn = 2010;
const int inf = 100000000;
struct node{
int v;
int layer;
};
vector<node> adj[maxn];
void bfs(int s){
queue<node> q;
node start;
start.v=s;
start.layer=0;
q.push(start);
inq[start.v] = true;
while(!q.empty()){
node topnode = q.front();
q.pop();
int u = topnode.v;
for(int i=0;i<adj[u].size();i++){
node next = adj[u][i];
next.layer = topnode.layer+1;
if(inq[next.v]==false){
q.push(next);
inq[next.v] = true;
}
}
}
}2.4Forwards on Weibo
#include<cstdio>
#include<cmath>
#include<vector>
#include<map>
#include<cstring>
#include<queue>
#include<algorithm>
#include<iostream>
using namespace std;
const int maxv = 2010;
const int inf = 100000000;
struct node{
int id;
int layer;
};
vector<node> adj[maxv];
bool inq[maxv] = {false};
int bfs(int s,int l){
int numforward = 0;
queue<node> q;
node start;
start.id = s;
start.layer = 0;
q.push(start);
inq[start.id] = true;
while(!q.empty()){
node topnode = q.front();
q.pop();
int u = topnode.id;
for(int i=0;i<adj[u].size();i++){
node next = adj[u][i];
next.layer = topnode.layer+1;
if(inq[next.id]==false&&next.layer<=l){
q.push(next);
inq[next.id] = true;
numforward++;
}
}
}
return numforward;
}
int main(){
node user;
int n,l,numfollow,idfollow;
scanf("%d%d",&n,&l);
for(int i=1;i<=n;i++){
user.id=i;
scanf("%d",&numfollow);
for(int j=0;j<numfollow;j++){
scanf("%d",&idfollow);
adj[idfollow].push_back(user);
}
}
int numquery,s;
scanf("%d",&numquery);
for(int i=0;i<numquery;i++){
memset(inq,false,sizeof(inq));
scanf("%d",&s);
int numforward = bfs(s,l);
printf("%d\n",numforward);
}
return 0;
}3.Battle Over Cities
3.1图
#include<cstdio>
#include<cmath>
#include<vector>
#include<map>
#include<cstring>
#include<queue>
#include<algorithm>
#include<iostream>
using namespace std;
const int N = 1111;
vector<int> g[N];
bool vis[N];
int currentpoint;
void dfs(int v){
if(v==currentpoint) return;
vis[v] = true;
for(int i=0;i<g[v].size();i++){
if(vis[g[v][i]]==false){
dfs(g[v][i]);
}
}
}
int n,m,k;
int main(){
scanf("%d%d%d",&n,&m,&k);
for(int i=0;i<m;i++){
int a,b;
scanf("%d%d",&a,&b);
g[a].push_back(b);
g[b].push_back(a);
}
for(int query=0;query<k;query++){
scanf("%d",¤tpoint);
memset(vis,false,sizeof(vis));
int block=0;
for(int i=1;i<=n;i++){
if(i!=currentpoint&&vis[i]==false){
dfs(i);
block++;
}
}
printf("%d\n",block-1);
}
return 0;
}3.2并查集
#include<cstdio>
#include<cmath>
#include<vector>
#include<map>
#include<cstring>
#include<queue>
#include<algorithm>
#include<iostream>
using namespace std;
const int N = 1111;
vector<int> g[N];
int father[N];
bool vis[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 fab = findfather(b);
if(faa!=fab){
father[faa] = fab;
}
}
void init(){
for(int i=1;i<N;i++){
father[i] = i;
vis[i] = false;
}
}
int n,m,k;
int main(){
scanf("%d%d%d",&n,&m,&k);
for(int i=0;i<m;i++){
int a,b;
scanf("%d%d",&a,&b);
g[a].push_back(b);
g[b].push_back(a);
}
int currentpoint;
for(int query=0;query<k;query++){
scanf("%d",¤tpoint);
init();
for(int i=1;i<=n;i++){
for(int j=0;j<g[i].size();j++){
int u = i, v = g[i][j];
if(u==currentpoint||v==currentpoint) continue;
unions(u,v);
}
}
int block=0;
for(int i=1;i<=n;i++){
if(i==currentpoint) continue;
int fa_i = findfather(i);
if(vis[fa_i]==false){
block++;
vis[fa_i] = true;
}
}
printf("%d\n",block-1);
}
return 0;
}4.Deepest Root
#include<cstdio>
#include<cmath>
#include<vector>
#include<map>
#include<cstring>
#include<queue>
#include<algorithm>
#include<iostream>
using namespace std;
const int N = 100010;
vector<int> g[N];
bool isroot[N];
int father[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 fab= findfather(b);
if(faa!=fab){
father[faa] = fab;
}
}
void init(int n){
for(int i=1;i<=n;i++){
father[i] = i;
}
}
int calblock(int n){
int block = 0;
for(int i=1;i<=n;i++){
isroot[findfather(i)]=true;
}
for(int i=1;i<=n;i++){
block+=isroot[i];
}
return block;
}
int maxh=0;
vector<int> temp,ans;
void dfs(int u,int height,int pre){
if(height>maxh){
temp.clear();
temp.push_back(u);
maxh = height;
}else if(height==maxh){
temp.push_back(u);
}
for(int i=0;i<g[u].size();i++){
if(g[u][i]==pre) continue;
dfs(g[u][i],height+1,u);
}
}
int main(){
int n;
scanf("%d",&n);
init(n);
int a,b;
for(int i=1;i<n;i++){
scanf("%d%d",&a,&b);
g[a].push_back(b);
g[b].push_back(a);
unions(a,b);
}
int block = calblock(n);
if(block!=1){
printf("Error: %d components\n",block);
}else{
dfs(1,1,-1);
ans = temp;
dfs(ans[0],1,-1);
for(int i=0;i<temp.size();i++){
ans.push_back(temp[i]);
}
sort(ans.begin(),ans.end());
printf("%d\n",ans[0]);
for(int i=1;i<ans.size();i++){
if(ans[i]!=ans[i-1]){
printf("%d\n",ans[i]);
}
}
}
}