POJ 1330 Nearest Common Ancestors LCA
/********************* Template ************************/ #include <set> #include <map> #include <list> #include <cmath> #include <ctime> #include <deque> #include <queue> #include <stack> #include <bitset> #include <cstdio> #include <string> #include <vector> #include <cassert> #include <cstdlib> #include <cassert> #include <cstring> #include <sstream> #include <fstream> #include <numeric> #include <iomanip> #include <iostream> #include <algorithm> #include <functional> using namespace std; #define EPS 1e-8 #define DINF 1e15 #define MAXN 10050 #define MOD 1000000007 #define INF 0x7fffffff #define LINF 1LL<<60 #define PI 3.14159265358979323846 #define lson l,m,rt<<1 #define rson m+1,r,rt<<1|1 #define BUG cout<<"BUG! "<<endl #define ABS(a) ((a)>0?(a):(-a)) #define LINE cout<<"------------------ "<<endl #define FIN freopen("in.txt","r",stdin) #define FOUT freopen("out.txt","w",stdout) #define mem(a,b) memset(a,b,sizeof(a)) #define FOR(i,a,b) for(int i = a ; i < b ; i++) #define read(a) scanf("%d",&a) #define read2(a,b) scanf("%d%d",&a,&b) #define read3(a,b,c) scanf("%d%d%d",&a,&b,&c) #define write(a) printf("%d\n",a) #define write2(a,b) printf("%d %d\n",a,b) #define write3(a,b,c) printf("%d %d %d\n",a,b,c) #pragma comment (linker,"/STACK:102400000,102400000") template<class T> inline T L(T a) {return (a << 1);} template<class T> inline T R(T a) {return (a << 1 | 1);} template<class T> inline T lowbit(T a) {return (a & -a);} template<class T> inline T Mid(T a,T b) {return ((a + b) >> 1);} template<class T> inline T gcd(T a,T b) {return b ? gcd(b,a%b) : a;} template<class T> inline T lcm(T a,T b) {return a / gcd(a,b) * b;} template<class T> inline T Min(T a,T b) {return a < b ? a : b;} template<class T> inline T Max(T a,T b) {return a > b ? a : b;} template<class T> inline T Min(T a,T b,T c) {return min(min(a,b),c);} template<class T> inline T Max(T a,T b,T c) {return max(max(a,b),c);} template<class T> inline T Min(T a,T b,T c,T d) {return min(min(a,b),min(c,d));} template<class T> inline T Max(T a,T b,T c,T d) {return max(max(a,b),max(c,d));} template<class T> inline T mod(T x,T y) {y = ABS(y); return x >= 0 ? x % y : x % y + y;} template<class T> inline T mul_mod(T a,T b,T n) { T ret = 0,tmp = a % n; while(b){ if((b&1) && (ret+=tmp)>=n) ret -= n; if((b>>=1) && (tmp<<=1)>=n) tmp -= n; }return ret; } template<class T> inline T pow_mod(T a,T b,T n){ T ret = 1; a = a % n; while(b){ if (b&1) ret = mul_mod(ret,a,n); if (b>>=1) a = mul_mod(a,a,n); }return ret; } template<class T> inline T exGCD(T a, T b, T &x, T &y){ if(!b) return x = 1,y = 0,a; T res = exGCD(b,a%b,x,y),tmp = x; x = y,y = tmp - (a / b) * y; return res; } template<class T> inline T reverse_bits(T x){ x = (x >> 1 & 0x55555555) | ((x << 1) & 0xaaaaaaaa); x = ((x >> 2) & 0x33333333) | ((x << 2) & 0xcccccccc); x = (x >> 4 & 0x0f0f0f0f) | ((x << 4) & 0xf0f0f0f0); x = ((x >> 8) & 0x00ff00ff) | ((x << 8) & 0xff00ff00); x = (x >>16 & 0x0000ffff) | ((x <<16) & 0xffff0000); return x; } typedef long long LL; typedef unsigned long long ULL; //typedef __int64 LL; typedef unsigned __int64 ULL; /********************* By F *********************/ vector<int> G[MAXN]; int fa[MAXN]; int lev[MAXN]; int root; int n,u,v,T; void init(){ for(int i = 0 ; i < MAXN; i++) G[i].clear(); mem(fa,0); mem(lev,0); } void dfs(int u,int dep){ lev[u] = dep; for(int i = 0 ; i < G[u].size() ; i++){ dfs(G[u][i],dep+1); } } int lca(int a,int b){ while(lev[a] > lev[b]) a = fa[a]; while(lev[a] < lev[b]) b = fa[b]; while(a != b){ a = fa[a]; b = fa[b]; } return a; } int main(){ //FIN; //FOUT; scanf("%d",&T); while(T--){ scanf("%d",&n); init(); for(int i = 0 ; i < n-1 ; i++){ scanf("%d%d",&u,&v); G[u].push_back(v); fa[v] = u; } scanf("%d%d",&u,&v); root = u; while(fa[root] != 0) root = fa[root]; dfs(root,1); printf("%d\n",lca(u,v)); } return 0; }
水题,没什么可说的