tarjan求LCA模板
废话不多说，模板拿来。
1 # include <iostream> 2 # include <cstdio> 3 # include <cstring> 4 # include <string> 5 # include <cmath> 6 # include <vector> 7 # include <map> 8 # include <queue> 9 # include <cstdlib> 10 # define MAXN 500001 11 using namespace std; 12 13 inline int get_num() { 14 int k = 0, f = 1; 15 char c = getchar(); 16 for(; !isdigit(c); c = getchar()) if(c == '-') f = -1; 17 for(; isdigit(c); c = getchar()) k = k * 10 + c - '0'; 18 return k * f; 19 } 20 21 int n, m, s; 22 int fa[MAXN], qx[MAXN], qy[MAXN], ans[MAXN], f[MAXN]; 23 vector <int> vec[MAXN], q[MAXN]; 24 25 inline int find(int x) 26 { 27 return x == fa[x] ? x : fa[x] = find(fa[x]); 28 } 29 30 inline void dfs(int u) 31 { 32 int i, v; 33 fa[u] = u; 34 for(i = 0; i < vec[u].size(); i++) 35 { 36 v = vec[u][i]; 37 if(f[u] != v) f[v] = u, dfs(v); 38 } 39 for(i = 0; i < q[u].size(); i++) 40 if(f[v = u ^ qx[q[u][i]] ^ qy[q[u][i]]]) 41 ans[q[u][i]] = find(v); 42 fa[u] = f[u]; 43 } 44 45 int main() 46 { 47 int i, x, y; 48 n = get_num(); 49 m = get_num(); 50 s = get_num(); 51 for(i = 1; i < n; i++) 52 { 53 x = get_num(); 54 y = get_num(); 55 vec[x].push_back(y); 56 vec[y].push_back(x); 57 } 58 for(i = 1; i <= m; i++) 59 { 60 qx[i] = get_num(); 61 qy[i] = get_num(); 62 q[qx[i]].push_back(i); 63 q[qy[i]].push_back(i); 64 } 65 dfs(s); 66 for(i = 1; i <= m; i++) printf("%d\n", ans[i]); 67 return 0; 68 }
