//i'm gnona explode
#include <iostream>
#include <algorithm>
#include <vector>
#include <utility>
#include <cmath>
#include "dreaming.h"
/*
Global:
• PARENTS = vect. keeps track of parents
• COLORS = vect. keeps of visited nodes
• DIST = (vect of pair<int, int>). NODE X -> DISTANCE TO ROOT
• ADJ = (vect of v<pair<int,int>>). adjacency list of the OG graph
• max_distance = ll. used to identify tree diameter
• ending_vertex = int. NODE WHERE DFS ENDS
*/
using namespace std;
using ll = long long int;
vector<int> parents(1e6 + 5, -1);
vector<int> colors(1e6 + 5, 0);
vector<pair<int, int> > dist(1e6+5);
vector<vector<pair<int, int> > > adj(1e6+100);
int max_distance = -1;
int ending_vertex = -1;
void printDist(int n) {
for (int i = 0; i < n; i++) {
cout << "Vertex " << i << ": Distance = " << dist[i].first << endl;
}
}
void dfs(int vertex, int id){
//cout << "ITERATION: " << vertex << "\n";
//printDist(5);
//cout << "\n";
colors[vertex] = id;
if(dist[vertex].first >= max_distance){
max_distance = dist[vertex].first;
ending_vertex = vertex;
}
for(auto neighbour: adj[vertex]){
int next_vertex = neighbour.first;
int travel_time = neighbour.second;
if(colors[next_vertex] >= id){
continue;
}
parents[next_vertex] = vertex;
dist[next_vertex].first = dist[vertex].first + travel_time;
//dist[next_vertex].first = dist[vertex].first + travel_time;
dfs(next_vertex, id);
}
}
int travelTime(int n, int m, int l, int A[], int B[], int T[]){
for(int i = 0; i<m; i++){
//converting everything to be a part of the adj data struct i know better
int u = A[i];
int v = B[i];
int weight = T[i];
pair<int, int> x;
pair<int, int> y;
x.first = v;
x.second = weight;
y.first = u;
y.second = weight;
adj[u].push_back(x);
adj[v].push_back(y);
}
int R1 = -2e9+100;
int R2 = -2e9+100;
int R3 = -2e9+100;
int D1 = -2e9+100;
int radius = -1;
vector<int> diameter;
for(int i = 0; i<n; i++){
//ITERATING THROUGHOUT EACH VERTEX INSIDE THE GRAPH
if(colors[i] == 2){
continue;
}
dfs(i, 1);
//printDist(n);
//cout << "STARTS AT: " << ending_vertex << "\n";
parents[ending_vertex] = -1;
dist[ending_vertex].first = 0;
max_distance = -1;
dfs(ending_vertex, 2);
//cout << "\n------\n";
//cout << "ENDS AT: " << ending_vertex << "\n";
//printDist(n);
diameter.clear();
int p = ending_vertex;
diameter.push_back(p);
int sum_of_diameter = dist[ending_vertex].first;
while(p != -1){
diameter.push_back(parents[p]);
p = parents[p];
}
//extra -1 woopsie
diameter.pop_back();
//reverse to go from the actual start to end order that i just like idk
reverse(diameter.begin(), diameter.end());
radius = sum_of_diameter;
int d_size = diameter.size();
if(d_size==0){
ending_vertex = colors[i];
}
/*cout << "MAIN ROOT OF 2ND DFS: " << ending_vertex << "\n";
cout << "SUM OF DIAMETER: " << sum_of_diameter << "\n";
cout << "TREE DIAMETER\n";*/
D1 = max(D1, sum_of_diameter);
/*for(int j = 0; j<diameter.size(); j++){
cout << diameter[j] << " ";
}
cout << "\n";*/
for(int j=0; j<diameter.size(); j++){
int index = diameter[j];
//cout << "COMPARING: " << radius << " AND THE MAXIMUM OF " << dist[index].first << " " << sum_of_diameter - dist[index].first << "\n";
radius = min(radius, max(dist[index].first, sum_of_diameter - dist[index].first));
}
//cout << "RADIUS: " << radius << "\n";
if(radius > R1){
R3 = R2;
R2 = R1;
R1 = radius;
}
else if(radius > R2){
R3 = R2;
R2 = radius;
}
else if(radius > R3){
R3 = radius;
}
//cout << "\n~~~~\n";
}
/*cout << "TOP 3 MOST LARGEST OF RADII:\n";
cout << R1 << " " << R2 << " " << R3 << "\n";*/
if(n-m == 1){
return D1;
}
else if(n-m == 2){
return max(D1, R1+R2+l);
}
else{
return max(D1, max(R1+R2+l, R2+R3+ (2*l)));
}
//return 0;
}
/*
int main(){
n = # of vertices
m = # of edges
l = edge weight of new bridge
A = 1st endpoint
B = 2nd endpoint
T = 1st and 2nd's edge weight
int n, m, l;
cin >> n >> m >> l;
int A[n];
int B[n];
int T[n];
for(int i =0; i<m; i++){
int x, y, z;
cin >> x >> y >> z;
A[i] = x;
B[i] = y;
T[i] = z;
}
cout << travelTime(n, m, l, A, B, T);
}*/
