#include<bits/stdc++.h>
using namespace std;

int main(){
	int n,m,source;
	cin >> n >> m;
	vector<pair<int,int> > g[n+1]; 	// 1-indexed adjacency list for of graph

	int a,b,wt;
	for(int i = 0; i<m ; i++){
		cin >> a >> b >> wt;
		g[a].push_back(make_pair(b,wt));
		g[b].push_back(make_pair(a,wt));
	}	
	
	cin >> source;
	
	// Dijkstra's algorithm begins from here
	priority_queue<pair<int,int>,vector<pair<int,int> >,greater<pair<int,int> > > pq;// min-heap ; In pair => (dist,from)
	vector<int> distTo(n+1,INT_MAX); 	// 1-indexed array for calculating shortest paths; 
	
	distTo[source] = 0;
	pq.push(make_pair(0,source));	// (dist,from)
	
	while( !pq.empty() ){
		int dist = pq.top().first;
		int prev = pq.top().second;
		pq.pop();
		
		vector<pair<int,int> >::iterator it;
		for( it = g[prev].begin() ; it != g[prev].end() ; it++){
			int next = it->first;
			int nextDist = it->second;
			if( distTo[next] > distTo[prev] + nextDist){
				distTo[next] = distTo[prev] + nextDist;
				pq.push(make_pair(distTo[next], next));
			}
		}
		
	}
	
	cout << "The distances from source, " << source << ", are : \n";
	for(int i = 1 ; i<=n ; i++)	cout << distTo[i] << " ";
	cout << "\n";
	
	return 0;
}
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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
}