hdu 3078 Network lca

  1 #include <iostream>
  2 #include <vector>
  3 #include <cstdio>
  4 #include <cstring>
  5 #include <algorithm>
  6 #include <cmath>
  7 #include <map>
  8 #include <set>
  9 #include <string>
 10 #include <queue>
 11 #include <stack>
 12 #include <bitset>
 13 using namespace std;
 14 #define pb(x) push_back(x)
 15 #define ll long long
 16 #define mk(x, y) make_pair(x, y)
 17 #define lson l, m, rt<<1
 18 #define mem(a) memset(a, 0, sizeof(a))
 19 #define rson m+1, r, rt<<1|1
 20 #define mem1(a) memset(a, -1, sizeof(a))
 21 #define mem2(a) memset(a, 0x3f, sizeof(a))
 22 #define rep(i, n, a) for(int i = a; i<n; i++)
 23 #define fi first
 24 #define se second
 25 typedef pair<int, int> pll;
 26 const double PI = acos(-1.0);
 27 const double eps = 1e-8;
 28 const int mod = 1e9+7;
 29 const int inf = 1061109567;
 30 const int dir[][2] = { {-1, 0}, {1, 0}, {0, -1}, {0, 1} };
 31 const int maxn = 1e5+5;
 32 int head[maxn*2], num, f[maxn], deep[maxn], n, val[maxn];
 33 struct node
 34 {
 35     int to, nextt;
 36 }e[maxn*2];
 37 void add(int u, int v) {
 38     e[num].to = v, e[num].nextt = head[u], head[u] = num++;
 39 }
 40 void init() {
 41     num = 0;
 42     mem1(head);
 43 }
 44 void dfs(int u, int fa) {
 45     f[u] = fa;
 46     for(int i = head[u]; ~i; i = e[i].nextt) {
 47         int v = e[i].to;
 48         if(v == fa)
 49             continue;
 50         deep[v] = deep[u]+1;
 51         dfs(v, u);
 52     }
 53 }
 54 int lca(int k, int a, int b)
 55 {
 56     int i,j;
 57     vector <int> v;
 58     if(deep[a]<deep[b])
 59         swap(a, b);
 60     while(deep[a]>deep[b]) {
 61         v.pb(val[a]);
 62         a = f[a];
 63     }
 64     while(a!=b) {
 65         v.pb(val[a]);
 66         v.pb(val[b]);
 67         a = f[a];
 68         b = f[b];
 69     }
 70     v.pb(val[a]);
 71     if(k>v.size())
 72         return -1;
 73     sort(v.begin(), v.end());
 74     reverse(v.begin(), v.end());
 75     return v[k-1];
 76 }
 77 int main()
 78 {
 79     int x, y, m, w, z, sign;
 80     while(cin>>n>>m) {
 81         init();
 82         for(int i = 1; i<=n; i++)
 83             scanf("%d", &val[i]);
 84         for(int i = 0; i<n-1; i++) {
 85             scanf("%d%d", &x, &y);
 86             add(x, y);
 87             add(y, x);
 88         }
 89         dfs(1, 0);
 90         while(m--) {
 91             scanf("%d%d%d", &sign, &x, &y);
 92             if(!sign) {
 93                 val[x] = y;
 94             } else {
 95                 int ans = lca(sign, x, y);
 96                 if(~ans)
 97                     cout<<ans<<endl;
 98                 else
 99                     puts("invalid request!");
100             }
101         }
102     }
103     return 0;
104 }