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94 changes: 94 additions & 0 deletions Dijkstra's Algorithm
Original file line number Diff line number Diff line change
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#include <bits/stdc++.h>
using namespace std;

#define debug(x) cout<<#x<<" is "<<endl

using ll = long long;

#define x first
#define y second

template <typename T>
struct Dijkstra {

int node,edge;
vector< vector< pair<int,T> > > adj;
vector< T > level;
vector<int> parent;

Dijkstra(int _node, int _edge) : node(_node), edge(_edge) {
vector<int>(node+1).swap(parent);
vector<T>(node+1, numeric_limits<T>::max()).swap(level);
vector< vector< pair<int,T> > > (node+1).swap(adj);
}

void add_edge(int u, int v, T w) {
adj[u].push_back({v,w});
adj[v].push_back({u,w});
}

void traverse(int src) {

level[src] = 0;
set< pair<T,int> > s {{0,src}};
parent[src] = -1;

while(not s.empty()) {
auto it = *s.begin();
int cur_node = it.y;
T cur_level = it.x;
s.erase(s.begin());

for(auto u : adj[cur_node]) {
if(level[u.x] - u.y > cur_level) {
level[u.x] = cur_level + u.y;
parent[u.x] = cur_node;
s.insert({level[u.x],u.x});
}
}
}
}

void print_path(int x) {

if(level[x] == numeric_limits<T>::max()) {
cout<<"-1\n";
return;
}

if(x == -1){
return;
}

print_path(parent[x]);
cout<<x<<" ";

}

};


int main(int argc, char const *argv[])
{
ios::sync_with_stdio(false);
cin.tie(nullptr);


int node,edge;
cin>>node>>edge;

Dijkstra<ll> d(node,edge);


while(edge--){
int x,y;
ll w;
cin>>x>>y>>w;
d.add_edge(x,y,w);
}

d.traverse(1);
d.print_path(node);

return 0;
}