#include <bits/stdc++.h>
using namespace std;
typedef vector<tuple<int, int, int>> vt;
typedef vector<pair<int, int>> vp;

// Input:
// Objects as (profit, weight, ratio) pairs
// objects[] = {{60, 10, 0}, {100, 20, 0}, {120, 30, 0}}
// Knapsack Capacity, M = 50;

// Output:
// Maximum possible profit = 240
// by taking objects of weight 10 and 20 kg and 2/3 fraction
// of 30 kg. Hence total profit will be 60+100+(2/3)(120) = 240

void profitByWeight(vt &objects)
{
    for (int i = 0; i < objects.size(); i++)
    {
        get<2>(objects[i]) = get<0>(objects[i]) / get<1>(objects[i]);
    }
}

bool sortByRatio(tuple<int, int, int> &a, tuple<int, int, int> &b)
{
    return (get<2>(a) > get<2>(b));
}

void print(vp choice, int maxProfit)
{
    cout << "Maximum possible profit = " << maxProfit << endl;
    cout << "Weights\t"
         << "Profits" << endl;
    for (int i = 0; i < choice.size(); i++)
    {
        cout << choice[i].first << '\t' << choice[i].second << endl;
    }
}

void solution(vt objects, int M)
{
    int maxProfit = 0;
    vp choice;

    for (int i = 0; i < objects.size(); i++)
    {
        if (M > 0 && get<1>(objects[i]) <= M)
        {
            M -= get<1>(objects[i]);
            maxProfit += get<0>(objects[i]);
            choice.push_back(make_pair(get<1>(objects[i]), get<0>(objects[i])));
        }
        else
        {
            int fraction = (M * get<0>(objects[i])) / get<1>(objects[i]);
            maxProfit += fraction;
            choice.push_back(make_pair(get<1>(objects[i]), fraction));
            break;
        }
    }

    print(choice, maxProfit);
}

int main()
{
    vt objects;
    objects.push_back(make_tuple(120, 30, 0));
    objects.push_back(make_tuple(100, 20, 0));
    objects.push_back(make_tuple(60, 10, 0));

    int M = 50;

    // Calculate profit/weight ratio
    profitByWeight(objects);

    // Sort in descending order of ratio
    sort(objects.begin(), objects.end(), sortByRatio);

    // Solution
    solution(objects, M);

    return 0;
}
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Read inputs from stdin

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

int main() 
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    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
}