Added Parallel Binary Search

Author: rachitkewl

Miscellanious/parallel_binary_search.cpp

@@ -0,0 +1,121 @@
+//http://agc002.contest.atcoder.jp/tasks/agc002_d
+#include <bits/stdc++.h>
+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;i<n;i++)
+#define ll long long
+#define si(x)	scanf("%d",&x)
+#define sl(x)	scanf("%I64d",&x)
+#define ss(s)	scanf("%s",s)
+#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>	pll;
+typedef vector<int>		vi;
+typedef vector<ll>		vl;
+typedef vector<pii>		vpii;
+typedef vector<pll>		vpll;
+typedef vector<vi>		vvi;
+typedef vector<vl>		vvl;
+const int mod = 1000000007;
+const ll N = 3e5;
+vi g[N];
+pii E[N];
+int mpow(int base, int exp); 
+void ipgraph(int n, int m);
+void dfs(int u, int par);
+struct node{
+	int i, a, b, z;
+};
+int T, n, m, ans[N], rep[N], sz[N];
+vector<node> Q;
+int get(int x){
+	if (x == rep[x]) return x;
+	return rep[x] = get(rep[x]);
+}
+void merge(int x, int y){
+	x = get(x);
+	y = get(y);
+	if (x == y) return;
+	if (sz[x] < sz[y]) rep[x] = y, sz[y] += sz[x];
+	else if (sz[x] > sz[y]) rep[y] = x, sz[x] += sz[y];
+	else rep[x] = y, sz[y]+=sz[x];
+}
+void init(){
+	int i;
+	T = 0;
+	Fo(i, 1, n+1) rep[i] = i, sz[i] = 1;
+}
+int go(int x, int y){
+	x = get(x), y = get(y);
+	if (x == y) return sz[x];
+	return sz[x] + sz[y];
+}
+void solve(){
+	queue< tuple<int, int, vector<node>> > q;
+	vector<node> query;
+	q.push(make_tuple(0, m, Q));
+	int L, R, i;
+	while(!q.empty()){
+		
+		tie(L, R, query) = q.front(); q.pop();
+		if (L+1 == R){
+			for(auto it: query)
+				ans[it.i] = R;
+			continue;
+		}
+		int mid = (L+R)/2;
+		vector<node> left, right; left.clear(); right.clear();
+		//execute till mid
+		if (T > mid){
+			init();
+			T = 0;
+		}
+		Fo(i, T+1, mid+1){
+			merge(E[i].F, E[i].S);
+		}
+		T = mid;
+		//update range for each query
+		for(auto it: query){
+			if (go(it.a, it.b) >= it.z) left.pb(it);
+			else right.pb(it);
+		}
+		
+		q.push(make_tuple(L, mid, left));
+		q.push(make_tuple(mid, R, right));
+	}
+	
+}
+int main()
+{
+	ios_base::sync_with_stdio(false);
+	cin.tie(NULL);
+	int i,k,j,u,v,w;
+	cin>>n>>m;
+	fo(i, m){
+		cin>>u>>v;
+		g[u].pb(v);
+		g[v].pb(u);
+		E[i+1] = {u, v};
+	}
+	int q;
+	cin>>q;
+	Fo(i, 1, q+1){
+		cin>>u>>v>>w;
+		Q.pb({i, u, v, w});
+	}
+	init();
+	solve();
+        Fo(i, 1, q+1)
+		cout<<ans[i]<<endl;
+	
+	return 0;
+}