Create 1724.Checking-Existence-of-Edge-Length-Limited-Paths-II.cpp

Author: wisdompeak

Union_Find/1724.Checking-Existence-of-Edge-Length-Limited-Paths-II/1724.Checking-Existence-of-Edge-Length-Limited-Paths-II.cpp

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+class DistanceLimitedPathsExist {
+ vector<pair<int,int>> snaps[10000];
+ int father[10000];
+ int rank[10000];
+ vector<int>dist;
+ unordered_set<int>changed;
+ int snapId = 0;
+public:
+ DistanceLimitedPathsExist(int n, vector<vector<int>>& edgeList) 
+ {
+ for (int i=0; i<n; i++)
+ {
+ snaps[i].push_back({-1, i});
+ father[i] = i;
+ } 
+ 
+ sort(edgeList.begin(),edgeList.end(), [](auto const &a,auto const &b) { return a[2] < b[2]; });
+ 
+ int cur_dist = 0;
+ for (auto e: edgeList)
+ {
+ if (e[2] > cur_dist) 
+ {
+ dist.push_back(cur_dist);
+ cur_dist = e[2];
+ for (auto node: changed)
+ {
+ snaps[node].push_back({snapId, father[node]});
+ }
+ changed.clear();
+ snapId++;
+ }
+ int a = e[0], b = e[1];
+ Union(a,b); 
+ }
+ }
+ 
+ int findFather(int node)
+ {
+ while (father[node]!=node)
+ node = father[node];
+ return node;
+ }
+ 
+ void Union(int a, int b)
+ {
+ a = findFather(a);
+ b = findFather(b);
+ if (findFather(a)!=findFather(b))
+ {
+ if (rank[a]<rank[b])
+ {
+ father[a] = b;
+ rank[b] = max(rank[b], rank[a]+1);
+ changed.insert(a);
+ }
+ else
+ {
+ father[b] = a;
+ rank[a] = max(rank[a], rank[b]+1);
+ changed.insert(b);
+ }
+ } 
+ }
+ 
+ int findSnapFather(int node, int snap_id)
+ {
+ auto iter = upper_bound(snaps[node].begin(), snaps[node].end(), make_pair(snap_id, INT_MAX));
+ iter = prev(iter,1);
+ int f = iter->second;
+ if (f==node)
+ return f;
+ else
+ return findSnapFather(f, snap_id); 
+ }
+ 
+ bool query(int p, int q, int limit) 
+ {
+ int snap_id = lower_bound(dist.begin(), dist.end(), limit) - dist.begin() - 1;
+ return findSnapFather(p, snap_id)==findSnapFather(q, snap_id);
+ }
+};
+
+/**
+ * Your DistanceLimitedPathsExist object will be instantiated and called as such:
+ * DistanceLimitedPathsExist* obj = new DistanceLimitedPathsExist(n, edgeList);
+ * bool param_1 = obj->query(p,q,limit);
+ */