求割点个数
/* gyt
Live up to every day */
#include<cstdio>
#include<cmath>
#include<iostream>
#include<algorithm>
#include<vector>
#include<stack>
#include<cstring>
#include<queue>
#include<set>
#include<string>
#include<map>
#include <time.h>
#define PI acos(-1)
using namespace std;
typedef long long ll;
typedef double db;
const int maxn = 4000+10;
const ll maxm = 1e7;
const int modd = 10000007;
const int INF = 1<<30;
const db eps = 1e-9;
struct Edge{
int u, v, next;
}e[maxn*4];
int n, m, cnt,scnt, tot;
stack<int>sta;
int dfn[maxn], low[maxn], vis[maxn], head[maxn];
int a[maxn], iscut[maxn], father[maxn];
void init() {
memset(head, -1, sizeof(head));
memset(dfn, 0, sizeof(dfn));
memset(low, 0, sizeof(low));
memset(vis, 0, sizeof(vis));
memset(iscut, 0, sizeof(iscut));
memset(father, 0, sizeof(father));
while(!sta.empty()) sta.pop();
cnt=0;
scnt=0; tot=0;
}
void add(int u, int v) {
e[cnt].v=v, e[cnt].next=head[u];
head[u]=cnt++;
}
void Tarjan(int s, int fa) {
int minn, t;
father[s]=fa;
dfn[s]=low[s]=++tot;
vis[s]=2;
sta.push(s);
for (int i=head[s]; ~i; i=e[i].next) {
int t=e[i].v;
if (!dfn[t]) {
Tarjan(t, s);
low[s]=min(low[s], low[t]);
} else {
if (vis[t]==2) {
low[s]=min(low[s], dfn[t]);
}
}
}
}
void solve() {
while(scanf("%d", &n)!=EOF) {
if (!n) break;
init();
int u, v;
while(scanf("%d",&u) && u){
while(getchar()!=‘\n‘){
scanf("%d",&v);
add(u,v);
add(v,u);
}
}
Tarjan(1, 0);
int rootson=0;
for (int i=2; i<=n; i++) {
int k=father[i];
if (k==1) rootson++;
else {
if (low[i]>=dfn[k]) {
iscut[k]=1;
}
}
}
if (rootson>1) iscut[1]=1;
int ans=0;
for (int i=1; i<=n; i++) {
if (iscut[i]) ans++;
}
printf("%d\n", ans);
}
}
int main() {
int t = 1;
//freopen("in.txt", "r", stdin);
//scanf("%d", &t);
while(t--)
solve();
return 0;
}
是否联通
/* gyt
Live up to every day */
#include<cstdio>
#include<cmath>
#include<iostream>
#include<algorithm>
#include<vector>
#include<stack>
#include<cstring>
#include<queue>
#include<set>
#include<string>
#include<map>
#include <time.h>
#define PI acos(-1)
using namespace std;
typedef long long ll;
typedef double db;
const int maxn = 100000+10;
const ll maxm = 1e7;
const int modd = 10000007;
const int INF = 1<<30;
const db eps = 1e-9;
struct Edge{
int u, v, next;
}e[maxn];
int n, m, cnt,scnt, tot;
stack<int>sta;
int dfn[maxn], low[maxn], vis[maxn], head[maxn];
void init() {
memset(head, -1, sizeof(head));
memset(dfn, 0, sizeof(dfn));
memset(low, 0, sizeof(low));
memset(vis, 0, sizeof(vis));
while(!sta.empty()) sta.pop();
cnt=0;
scnt=0; tot=0;
}
void add(int u, int v) {
e[cnt].v=v, e[cnt].next=head[u];
head[u]=cnt++;
}
void Tarjan(int s) {
int minn, t;
dfn[s]=low[s]=++tot;
vis[s]=2;
sta.push(s);
for (int i=head[s]; ~i; i=e[i].next) {
int t=e[i].v;
if (!dfn[t]) {
Tarjan(t);
low[s]=min(low[s], low[t]);
} else {
if (vis[t]==2) {
low[s]=min(low[s], dfn[t]);
}
}
}
if (low[s]==dfn[s]) {
scnt++;
while(!sta.empty()) {
int t=sta.top();
sta.pop();
vis[t]=1;
if (t==s) break;
}
}
}
void solve() {
while(scanf("%d%d", &n, &m)!=EOF) {
if (!n&&!m) break;
init();
for (int i=0; i<m; i++) {
int a, b; scanf("%d%d", &a, &b);
add(a, b);
}
for (int i=1; i<=n; i++) {
if (!dfn[i]) Tarjan(i);
}
if (scnt==1) puts("Yes");
else puts("No");
}
}
int main() {
int t = 1;
//freopen("in.txt", "r", stdin);
//scanf("%d", &t);
while(t--)
solve();
return 0;
}
缩点
/* gyt
Live up to every day */
#include<cstdio>
#include<cmath>
#include<iostream>
#include<algorithm>
#include<vector>
#include<stack>
#include<cstring>
#include<queue>
#include<set>
#include<string>
#include<map>
#include <time.h>
#define PI acos(-1)
using namespace std;
typedef long long ll;
typedef double db;
const int maxn = 4000+10;
const ll maxm = 1e7;
const int modd = 10000007;
const int INF = 1<<30;
const db eps = 1e-9;
struct Edge{
int u, v, next;
}e[maxn*4];
int n, m, cnt,scnt, tot;
stack<int>sta;
int dfn[maxn], low[maxn], vis[maxn], head[maxn];
int du[maxn], color[maxn];
int a[maxn], in[maxn];
void init() {
memset(head, -1, sizeof(head));
memset(dfn, 0, sizeof(dfn));
memset(low, 0, sizeof(low));
memset(vis, 0, sizeof(vis));
memset(du, 0, sizeof(du));
memset(color, 0, sizeof(color));
for (int i=0; i<maxn; i++) in[i]=INF;
while(!sta.empty()) sta.pop();
cnt=0;
scnt=0; tot=0;
}
void add(int u, int v) {
e[cnt].v=v, e[cnt].next=head[u];
head[u]=cnt++;
}
void Tarjan(int s) {
int minn, t;
dfn[s]=low[s]=++tot;
vis[s]=2;
sta.push(s);
for (int i=head[s]; ~i; i=e[i].next) {
int t=e[i].v;
if (!dfn[t]) {
Tarjan(t);
low[s]=min(low[s], low[t]);
} else {
if (vis[t]==2) {
low[s]=min(low[s], dfn[t]);
}
}
}
if (low[s]==dfn[s]) {
scnt++;
while(!sta.empty()) {
int t=sta.top();
sta.pop();
vis[t]=1;
color[t]=scnt;
if (t==s) break;
}
}
}
void solve() {
while(scanf("%d%d", &n, &m)!=EOF) {
for (int i=1; i<=n; i++) {
scanf("%d", a+i);
}
init();
for (int i=0; i<m; i++) {
int a, b; scanf("%d%d", &a, &b);
add(a, b);
}
for (int i=1; i<=n; i++) {
if (!dfn[i]) Tarjan(i);
}
for (int u=1; u<=n; u++) {
for (int i=head[u]; ~i; i=e[i].next) {
int v=e[i].v;
if (color[u]!=color[v]) {
du[color[v]]++;
}
}
}
int ans=0, ansnum=0;
for (int i=1; i<=scnt; i++) {
if (!du[i]) {
ans++;
int num=INF;
for (int j=1; j<=n; j++) {
if (color[j]==i) {
in[i]=min(a[j], in[i]);
}
}
ansnum+=in[i];
}
}
printf("%d %d\n", ans, ansnum);
}
}
int main() {
int t = 1;
//freopen("in.txt", "r", stdin);
//scanf("%d", &t);
while(t--)
solve();
return 0;
}
时间： 2024-10-05 02:00:05