#include <iostream>
#include <vector>
#include <deque>
#include <climits>

using namespace std;

struct Edge {
    int to, weight;
};


struct State {
    int node, cost, coupons;
};


int minTravelCost(int n, int m, vector<vector<Edge>>& graph) {
    vector<vector<int>> minCost(n, vector<int>(3, INT_MAX)); 
    deque<State> dq; 
    dq.push_back({0, 0, 2});
    minCost[0][2] = 0;

    while (!dq.empty()) {
        State curr = dq.front();
        dq.pop_front();

        if (curr.node == n - 1) {
            return curr.cost;
        }

        for (Edge& edge : graph[curr.node]) {
            int nextNode = edge.to;
            int nextCost = curr.cost + edge.weight;

            if (nextCost < minCost[nextNode][curr.coupons]) {
                minCost[nextNode][curr.coupons] = nextCost;
                dq.push_back({nextNode, nextCost, curr.coupons});
            }

            if (curr.coupons > 0) {
                int couponCost = curr.cost + 1;
                if (couponCost < minCost[nextNode][curr.coupons - 1]) {
                    minCost[nextNode][curr.coupons - 1] = couponCost;
                    dq.push_front({nextNode, couponCost, curr.coupons - 1});
                }
            }
        }
    }
    return -1; 
}

int main() {
    int n, m;
    cin >> n >> m;
    vector<vector<Edge>> graph(n);
    
    for (int i = 0; i < m; i++) {
        int u, v, w;
        cin >> u >> v >> w;
        graph[u - 1].push_back({v - 1, w});
        graph[v - 1].push_back({u - 1, w});
    }

    cout << minTravelCost(n, m, graph) << endl;
    return 0;
}

C++ Online Compiler

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Read inputs from stdin

OneCompiler's C++ online compiler supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample program which takes name as input and print your name with hello.

#include <iostream>
#include <string>
using namespace std;

int main() 
{
    string name;
    cout << "Enter name:";
    getline (cin, name);
    cout << "Hello " << name;
    return 0;
}

About C++

C++ is a widely used middle-level programming language.

  • Supports different platforms like Windows, various Linux flavours, MacOS etc
  • C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
  • Case-sensitive
  • C++ is a compiler based language
  • C++ supports structured programming language
  • C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
  • Like C, C++ also allows you to play with memory using Pointers.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
   //code
}
else {
   //code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression){    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
......    
    
default:     
 code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  //code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
// code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
 // code 
} while (condition);

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.

How to declare a Function:

return_type function_name(parameters);

How to call a Function:

function_name (parameters)

How to define a Function:

return_type function_name(parameters) {  
 // code
}