Assignment 1 submitted

Programming Task Solutions/Flight Discount.cpp

@@ -0,0 +1,73 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+#define int long long int
+
+int djikstramodified(int n, int m, unordered_map<int,list<pair<int,int>>> &adjList){
+    if(n==1) return 0;
+    vector<int>dist(n+1,LLONG_MAX);
+    vector<int>disc(n+1,LLONG_MAX);
+    priority_queue<pair<int,pair<int,int>>,vector<pair<int,pair<int,int>>>,greater<pair<int,pair<int,int>>>>pq;
+    pq.push({0,{1,0}}); dist[1]=0; 
+    while(!pq.empty()){
+        int d = pq.top().first;
+        int node = pq.top().second.first;
+        bool couponUsed = pq.top().second.second;
+        pq.pop();
+        if(couponUsed==0){
+            if(dist[node]<d){
+                continue;
+            }
+        }
+        else{
+            if(disc[node]<d){
+                continue;
+            }
+        }
+        for(auto i:adjList[node]){
+            int v = i.first; int c = i.second;
+            if(couponUsed==0){
+                //either preserve coupon
+                if((d+c)<dist[v]){
+                    dist[v]=d+c;
+                    pq.push({dist[v],{v,0}});
+                }
+                //or use it
+                if((d+c/2)<disc[v]){
+                    disc[v]=d+c/2;
+                    pq.push({disc[v],{v,1}});
+                }
+            }
+            else{
+                //you cant use coupon now and we will only be able to alter discounted price array
+                if((d+c)<disc[v]){
+                    disc[v]=d+c;
+                    pq.push({disc[v],{v,1}});
+                }
+            }
+        }
+    }
+    return disc[n];
+}
+
+void solve(){
+    int n; int m;
+    cin>>n>>m;
+    unordered_map<int,list<pair<int,int>>> adjList;
+    for(int i=0; i<m;i++){
+        int u, v, d;
+        cin>>u>>v>>d;
+        adjList[u].push_back({v,d});
+    }
+    cout<<djikstramodified(n,m,adjList)<<"\n";
+}
+
+signed main(){
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL); cout.tie(NULL);
+
+    solve();
+
+
+    return 0;
+}

Programming Task Solutions/Flight Routes.cpp

@@ -0,0 +1,52 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+#define int long long
+
+void solve(){
+    int n, m, k;
+    cin>>n>>m>>k;
+    vector<priority_queue<int>>dist(n+1);
+    unordered_map<int,list<pair<int,int>>>adjList;
+    for(int i=0;i<m;i++){
+        int u, v, d; cin>>u>>v>>d;
+        adjList[u].push_back({v,d});
+    }
+
+    priority_queue<pair<int,int>,vector<pair<int,int>>,greater<pair<int,int>>>pq;
+    pq.push({0,1}); dist[1].push(0);
+    while(!pq.empty()){
+        int d = pq.top().first;
+        int node = pq.top().second;
+        pq.pop();
+        if(d>dist[node].top()) continue;
+        for(auto i:adjList[node]){
+            if(dist[i.first].size()<k){
+                dist[i.first].push(d+i.second);
+                pq.push({d+i.second,i.first});
+            }
+            else if((d+i.second<dist[i.first].top())){
+                dist[i.first].push(d+i.second);
+                dist[i.first].pop();
+                pq.push({d+i.second,i.first});
+            }
+        }
+    }
+    vector<int>ans;
+    while(!dist[n].empty()){
+        ans.push_back(dist[n].top());
+        dist[n].pop();
+    }
+    reverse(ans.begin(),ans.end());
+    for(int i=0; i<k; i++){
+        cout<<ans[i]<<" ";
+    } cout<<"\n";
+}
+
+signed main(){
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL); cout.tie(NULL);
+
+    solve();
+
+}

Programming Task Solutions/Shortest Routes I.cpp

@@ -0,0 +1,44 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+#define int long long
+
+void solve(){
+    int n; int m;
+    cin>>n>>m;
+    unordered_map<int,list<pair<int,int>>> adjList;
+    for(int i=0; i<m;i++){
+        int u, v, d;
+        cin>>u>>v>>d;
+        adjList[u].push_back({v,d});
+    }
+    vector<int>dist(n+1,LLONG_MAX);
+    priority_queue<pair<int,int>,vector<pair<int,int>>,greater<pair<int,int>>>pq;
+    pq.push({0,1}); dist[1]=0; 
+    while(!pq.empty()){
+        int d = pq.top().first;
+        int node = pq.top().second;
+        pq.pop();
+        if(dist[node]<d) continue;
+        for(auto i:adjList[node]){
+            if(dist[i.first]>(d+i.second)){
+                dist[i.first]=d+i.second;
+                pq.push({dist[i.first],i.first});
+            }
+        }
+    }
+    for(int i=1;i<=n;i++){
+        cout<<dist[i]<<" ";
+    } cout<<"\n";
+
+}
+
+signed main(){
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL); cout.tie(NULL);
+
+    solve();
+
+
+    return 0;
+}

Programming Task Solutions/Shortest Routes II.cpp

@@ -0,0 +1,47 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+#define int long long int
+
+void solve(){
+    int n, m, q;
+    cin>>n>>m>>q;
+    vector<vector<int>>dist(n+1,vector<int>(n+1,1e13));
+    for(int i=0;i<m;i++){
+        int u, v, d; cin>>u>>v>>d;
+        dist[u][v]=min(d,dist[u][v]);
+        dist[v][u]=min(d,dist[v][u]);
+    }
+    for(int i=1;i<=n;i++){
+        dist[i][i]=0;
+    }
+
+    for(int k=1; k<=n; k++){
+        for(int i=1;i<=n;i++){
+            for(int j=1;j<=n;j++){
+                if(i==k||j==k || i==j) continue;
+                if(dist[i][k]==1e13 || dist[k][j]==1e13) continue;
+                dist[i][j]=min(dist[i][j],dist[i][k]+dist[k][j]);
+            }
+        }
+    }
+
+    for(int i=0;i<q;i++){
+        int u,v;
+        cin>>u>>v;
+        if(dist[u][v]==1e13){
+            cout<<-1<<"\n";
+        }
+        else{
+            cout<<dist[u][v]<<"\n";
+        }
+    }
+}
+
+signed main(){
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL); cout.tie(NULL);
+
+    solve();
+
+}