adding Greedy problems

Adding problems related to greedy approach
1. Activity Selection Problem
2.Fractional Knapsack Problem
3.Huffman Algorithm
4.Job Sequencing Problem
5.Minimum Coin Problem

Author: KhushiSahoo

Greedy/HuffmanAlgorithm.cpp

@@ -0,0 +1,80 @@
+
+#include <bits/stdc++.h>
+using namespace std;
+
+// A Huffman tree node
+struct Node {
+	char data;
+	unsigned freq;
+	Node *left, *right;
+
+	Node(char data, unsigned freq, Node* l = NULL, Node* r = NULL)
+ 
+	{
+
+		this->left = l;
+		this->right = r;
+		this->data = data;
+		this->freq = freq;
+	}
+};
+
+// For comparison 
+struct compare {
+
+	bool operator()(Node* l, Node* r)
+
+	{
+		return (l->freq > r->freq);
+	}
+};
+
+// Prints huffman codes from
+void printCodes(struct Node* root, string str)
+{
+
+	if (!root)
+		return;
+
+	if (root->data != '$')
+		cout << root->data << ": " << str << "\n";
+
+	printCodes(root->left, str + "0");
+	printCodes(root->right, str + "1");
+}
+
+void printHcodes(char arr[], int freq[], int size)
+{
+
+	priority_queue<Node*, vector<Node*>, compare> h;
+
+	for (int i = 0; i < size; ++i)
+		h.push(new Node(arr[i], freq[i]));
+
+	while (h.size() > 1) {
+
+		Node *l = h.top();h.pop();
+
+		Node *r = h.top();h.pop();
+
+	
+		Node *top = new Node('$', l->freq + r->freq, l, r);
+
+		h.push(top);
+	}
+	printCodes(h.top(), "");
+}
+
+int main()
+{
+
+	char arr[] = { 'a', 'd', 'e', 'f' };
+	int freq[] = { 30, 40, 80, 60 };
+
+	int size = sizeof(arr) / sizeof(arr[0]);
+
+	printHcodes(arr, freq, size);
+
+	return 0;
+}
+

Greedy/activitySelectionProblem.cpp

@@ -0,0 +1,38 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+bool myCmp(pair <int, int> a, pair <int, int> b)
+{
+	return (a.second < b.second);
+}
+
+int maxActivities(pair <int, int> arr[], int n)
+{
+	sort(arr, arr + n, myCmp);
+
+	int prev = 0;
+	int res = 1;
+
+	for(int curr = 1; curr < n; curr++)
+	{
+	 
+		if(arr[curr].first >= arr[prev].second)
+		{
+			res++;
+
+			prev = curr;
+		}
+	}
+
+	return res;
+}
+int main()
+{
+	pair <int, int> arr[] = {make_pair(12, 25), make_pair(10, 20), make_pair(20, 30)};
+
+	int n = 3;
+
+	cout<<maxActivities(arr, n); 
+
+	return 0;
+}

Greedy/fractionalKnapsack.cpp

@@ -0,0 +1,47 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+bool myCmp(pair <int, int> a, pair <int, int> b)
+{
+	double r1 = (double)a.first / a.second;
+
+	double r2 = (double)b.first / b.second;
+
+	return r1 > r2;
+}
+
+double fKnapS(int W, pair <int, int> arr[], int n)
+{
+	sort(arr, arr + n, myCmp);
+
+	double  res = 0.0;
+
+	for(int i = 0; i < n; i++)
+	{
+		if(arr[i].second <= W)
+		{
+			res += arr[i].first;
+
+			W = W - arr[i].second;
+		}
+		else
+		{
+			res += arr[i].first * ((double) W / arr[i].second);
+
+			break;
+		}
+	}
+
+
+	return res;
+}
+int main()
+{
+	pair <int, int> arr[] = {make_pair(120, 30), make_pair(100, 20), make_pair(60, 10)};
+
+	int n = 3, W = 50;
+
+	cout<<fKnapS(W, arr, n); 
+
+	return 0;
+}

Greedy/jobSequencing.cpp

@@ -0,0 +1,65 @@
+// Program to find the maximum profit job sequence from a given array
+// of jobs with deadlines and profits
+#include<iostream>
+#include<algorithm>
+using namespace std;
+  
+// A structure to represent a job
+struct Job
+{
+   char id;     
+   int dead;   
+   int profit;  
+};
+  
+// sorting all jobs according to profit
+bool comparison(Job a, Job b)
+{
+     return (a.profit > b.profit);
+}
+  
+// Returns minimum number of platforms required
+void printJobScheduling(Job arr[], int n)
+{
+   
+    sort(arr, arr+n, comparison);
+  
+    int result[n]; 
+    bool slot[n];  
+    
+    for (int i=0; i<n; i++)
+        slot[i] = false;
+  
+    
+    for (int i=0; i<n; i++)
+    {
+       
+       for (int j=min(n, arr[i].dead)-1; j>=0; j--)
+       {
+          
+          if (slot[j]==false)
+          {
+             result[j] = i;  
+             slot[j] = true; 
+             break;
+          }
+       }
+    }
+  
+    
+    for (int i=0; i<n; i++)
+       if (slot[i])
+         cout << arr[result[i]].id << " ";
+}
+  
+
+int main()
+{
+    Job arr[] = { {'a', 2, 100}, {'b', 1, 19}, {'c', 2, 27},
+                   {'d', 1, 25}, {'e', 3, 15}};
+    int n = sizeof(arr)/sizeof(arr[0]);
+    cout << "Following is maximum profit sequence of jobs \n";
+    
+    printJobScheduling(arr, n);
+    return 0;
+}

Greedy/minimumCoin.cpp

@@ -0,0 +1,38 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+
+int minCoins(int coin[], int n, int amount)
+{	
+    	sort(coin, coin + n);
+
+    	int res = 0;
+
+    	for(int i = n - 1; i >= 0; i--)
+    	{
+    		if(coin[i] <= amount)
+    		{
+    			int c = floor(amount / coin[i]);
+
+    			res = res + c;
+
+    			amount = amount - c * coin[i];
+    		}
+
+    		if(amount == 0)
+    			break;
+    	}
+
+    	return res;
+}
+    
+
+
+int main() {
+	
+      int coin[] = {5, 10, 2, 1}, n = 4, amount = 57;
+      
+      cout<<minCoins(coin, n, amount);
+
+    
+}