poj1419Graph Coloring(一般图最大独立集或着最大团)

// 最大独立集做法
vector<vector<int> > G;
int n, m;
int color[123];
vector<int> rec;
int maxnum;
void dfs(int u,int _count) {
if (_count > maxnum) {//更新答案
maxnum = _count;
rec.clear();
for (int i = 1;i <= n;++i) {
if (color[i]) rec.push_back(i);
}
}
if (u == n + 1) return ;
//用于判断是否可以染成黑色
bool ok = true;
for (int i = 0;i < G[u].size();++i) {
if (color[G[u][i]]) ok = false;
}

if (ok) {//u节点可以染成黑色
color[u] = 1;
dfs(u + 1, _count + 1);
color[u] = 0;
}
dfs(u + 1, _count);//u染成白色－>跳过

}
int main(int argc, const char * argv[])
{
// freopen("in.txt","r",stdin);
// freopen("out.txt","w",stdout);
// clock_t _ = clock();

int t, u, v;
cin >> t;
while(t--) {
scanf("%d%d", &n, &m);
G.clear();
G.resize(n + 2);
while(m--) {
scanf("%d%d", &u, &v);
G[u].push_back(v);
G[v].push_back(u);
}
memset(color, 0,sizeof color);
maxnum = 0;
dfs(1, 0);
printf("%d\n", maxnum);
for (int i = 0;i < rec.size();++i)
printf("%d%c", rec[i], i == maxnum - 1?'\n':' ');
}

// printf("\nTime cost: %.2fs\n", 1.0 * (clock() - _) / CLOCKS_PER_SEC);
return 0;
}

//最大团做法
int mp[123][123];
int rec[123];
int tmp[123];
int cnt, ans;
int n, m;
void dfs(int u) {
if (u == n + 1) {
if (cnt > ans)
ans = cnt;
memcpy(rec, tmp, sizeof tmp);
return ;
}
//判断u是否可以划入到这个团中去
bool ok = true;
for (int i = 1;i < u;++i) {
if (tmp[i] && mp[i][u]) {
ok = false;
break;
}
}

if (ok) {
tmp[u] = 1;cnt++;
dfs(u + 1);
tmp[u] = 0;cnt--;
}
//跳过u节点后判断下可行性
if (n + cnt - u > ans)
dfs(u + 1);
}
int main(int argc, const char * argv[])
{
// freopen("in.txt","r",stdin);
// freopen("out.txt","w",stdout);
// clock_t _ = clock();

int t;
cin >> t;
while(t--) {
scanf("%d%d", &n, &m);
memset(mp, 0,sizeof mp);
memset(tmp, 0,sizeof tmp);
int u, v;
for (int i = 1;i <= m;++i) {
scanf("%d%d", &u, &v);
mp[u][v] = mp[v][u] = 1;
}
cnt = ans = 0;
dfs(1);
printf("%d\n", ans);
bool first = true;
for (int i = 1;i <= n;++i) {
if (rec[i]) {
if (first) printf("%d", i);
else printf(" %d", i);
first = false;
}
}
printf("\n");
}

// printf("\nTime cost: %.2fs\n", 1.0 * (clock() - _) / CLOCKS_PER_SEC);
return 0;
}