Merge pull request rachitiitr#4 from rachitkewl/master

Added HLD code

Author: rachitiitr

Tree/HLD.cpp

@@ -0,0 +1,213 @@
+#include <bits/stdc++.h>
+// http://www.spoj.com/problems/QTREE/
+using namespace std;
+#define gc getchar_unlocked
+#define fo(i,n) for(i=0;i<n;i++)
+#define Fo(i,k,n) for(i=k;k<n?i<n:i>n;k<n?i+=1:i-=1)
+#define ll long long
+#define si(x)	scanf("%d",&x)
+#define sl(x)	scanf("%lld",&x)
+#define ss(s)	scanf("%s",s)
+#define pi(x)	printf("%d\n",x)
+#define pl(x)	printf("%lld\n",x)
+#define ps(s)	printf("%s\n",s)
+#define deb(x) cout << #x << "=" << x << endl
+#define deb2(x, y) cout << #x << "=" << x << "," << #y << "=" << y << endl
+#define pb push_back
+#define mp make_pair
+#define F first
+#define S second
+#define all(x) x.begin(), x.end()
+#define clr(x) memset(x, 0, sizeof(x))
+#define sortall(x) sort(all(x))
+#define tr(it, a) for(auto it = a.begin(); it != a.end(); it++)
+#define PI 3.1415926535897932384626
+typedef pair<int, int>	pii;
+typedef pair<ll, ll>	pl;
+typedef vector<int>		vi;
+typedef vector<ll>		vl;
+typedef vector<pii>		vpii;
+typedef vector<pl>		vpl;
+typedef vector<vi>		vvi;
+typedef vector<vl>		vvl;
+int mpow(int base, int exp); 
+void ipgraph(int m);
+void dfs(int u, int par);
+const int mod = 1000000007;
+const int N = 3e5, M = N;
+//=======================
+struct node{int v, w, i;};
+vector<node> g[N];
+int a[N], pos[N], arr[N];
+int sz[N], lvl[N], rep[N];
+int P[N][20], n;
+int chainNo, ptr;
+int chainOf[N], chainHead[N];
+int tree[4*N];
+
+void dfs(int u, int par){
+    sz[u] = 1;
+    lvl[u] = 1+lvl[par];
+    P[u][0] = par;
+	for(node to:g[u]){
+		int v = to.v;
+		if (v == par) continue;
+		rep[to.i] = v;
+		dfs(v, u);
+		sz[u] += sz[v];
+	}
+}
+
+int lca(int u, int v){
+    int i, lg;
+    if (lvl[u] < lvl[v]) swap(u, v);
+    for(lg = 0; (1<<lg) <= lvl[u]; lg++);
+    lg--;
+    for(i=lg; i>=0; i--){
+        if (lvl[u] - (1<<i) >= lvl[v])
+            u = P[u][i];
+    }
+    if (u == v) return u;
+    for(i=lg; i>=0; i--){
+        if (P[u][i] != -1 and P[u][i] != P[v][i])
+            u = P[u][i], v = P[v][i];
+    }
+    return P[u][0];
+}
+void init(){
+	int i, j;
+	Fo(i, 0, n+1) g[i].clear();
+	ptr = 0, chainNo = 1;
+	sz[0] = arr[0] = 0;
+	lvl[0] = -1;
+	Fo(i, 0, n+1) {
+		chainHead[i] = -1;
+		pos[i] = arr[i] = 0;
+		Fo(j, 0, 20) P[i][j] = -1;
+	}
+}
+int range_query(int rt, int lo, int hi, int x, int y){
+	if(lo == x and hi == y) return tree[rt];
+	int l = 2*rt, r = l+1, mid = (lo+hi)>>1;
+	if(y <= mid) return range_query(l, lo, mid, x, y);
+	if(x > mid) return range_query(r, mid+1, hi, x, y);
+	return max(range_query(l, lo, mid, x, mid), range_query(r, mid+1, hi, mid+1, y));
+}
+int query_up(int u, int v){
+	if(u == v) return 0;
+	if(lvl[u] < lvl[v]) swap(u, v);
+	int uchain, vchain = chainOf[v];
+	int ans = 0;
+	while(1){
+		uchain = chainOf[u];
+		if(uchain == vchain){
+			if(u == v) return ans;
+			ans = max(ans, range_query(1, 0, ptr, pos[v]+1, pos[u]));
+			return ans;
+		}
+		ans = max(ans, range_query(1, 0, ptr, pos[chainHead[uchain]], pos[u]));
+		u = chainHead[uchain];
+		u = P[u][0];
+	}
+	return ans;
+}
+void hld(int u, int cost, int par){
+	if(chainHead[chainNo] == -1) 
+		chainHead[chainNo] = u;
+	chainOf[u] = chainNo;
+	pos[u] = ++ptr;
+	arr[ptr] = cost;
+	int sc = 0, w;
+	for(node to: g[u]){
+		int v = to.v;
+		if(v == par) continue;
+		if(sz[sc] < sz[v])sc = v, w = to.w;
+ 	}
+	if(sc) hld(sc, w, u);
+	for(node to: g[u]){
+		int v = to.v;
+		if(v == par or v == sc) continue;
+		chainNo++;
+		hld(v, to.w, u);
+ 	}
+}
+void build(int rt, int lo, int hi){
+	if(lo == hi){
+		tree[rt] = arr[lo];
+		return;
+	}
+	int l = 2*rt, r = l+1, mid = (lo+hi)>>1;
+	build(l, lo, mid);
+	build(r, mid+1, hi);
+	tree[rt] = max(tree[l], tree[r]);
+}
+void update(int rt, int lo, int hi, int pos, int val){
+	if(lo == hi){
+		tree[rt] = val;
+		return;
+	}
+	int l = 2*rt, r = l+1, mid = (lo+hi)>>1;
+	if(pos<=mid) update(l, lo, mid, pos, val);
+	else update(r, 1+mid, hi, pos, val);
+	tree[rt] = max(tree[l], tree[r]);
+}
+
+int query(int u, int v){
+	int w = lca(u, v);
+	int ans = max(query_up(u, w), query_up(v, w));
+	return ans;
+}
+void change(int i, int val){
+	int u = rep[i];
+	update(1, 0, ptr, pos[u], val);
+}
+void compute(){
+	int i, j;
+	dfs(1, 0);
+	for(i=1; i<20; i++){
+        Fo(j, 1, n+1)
+            if (P[j][i-1] != -1)
+                P[j][i] = P[P[j][i-1]][i-1];
+	}
+	hld(1, 0, 0);
+	//make segment tree now
+	assert(ptr == n);
+	build(1, 0, ptr);
+}
+void solve(){
+	int i;
+	si(n);
+	init();
+	int u, v, w;
+	char s[10];
+	fo(i, n-1){
+		si(u);
+		si(v);
+		si(w);
+		g[u].pb({v, w, i+1});
+		g[v].pb({u, w, i+1});
+	}
+	compute();
+	ss(s);
+	while(1){
+		if(s[0] == 'D') break;
+		si(u); si(v);
+		if(s[0] == 'C'){
+			change(u, v);
+		}
+		else{
+			pi(query(u, v));
+		}
+		ss(s);
+	}
+}
+int main()
+{
+	ios_base::sync_with_stdio(false);
+	cin.tie(NULL);
+	int i,k,j;
+	int t;
+	si(t);
+	while(t--) solve();
+	return 0;
+}