Merge pull request #418 from coderdoze/master

Added huffman encoding

Author: probot-auto-merge[bot]

Dynamic Programming/Longest Common Subsequence/LCS_print_all.c++

@@ -0,0 +1,72 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+int dp[50][50];
+//use recursion to print all possible solutions
+//set to store the possible lcs in non-repeating and in increasing order(alphabetically)
+set<string> getAllLCS(string a,string b,int n,int m)
+{
+	set<string> ans;
+
+    if(n==0 || m==0)
+    {
+    	ans.insert("");
+    	return ans;
+    }
+
+	if(a[n-1]==b[m-1])
+	{
+		set<string> tmp=getAllLCS(a,b,n-1,m-1);
+		for(string s:tmp)
+			ans.insert(s+a[n-1]);
+
+	}
+
+
+	else
+	{
+		 if(dp[n-1][m]>=dp[n][m-1])
+		 	ans=getAllLCS(a,b,n-1,m);
+
+
+		 if(dp[n][m-1]>=dp[n-1][m])
+		 {
+		 	set<string> tmp=getAllLCS(a,b,n,m-1);
+
+		 	ans.insert(tmp.begin(),tmp.end());
+		 }
+	}
+
+	return ans;
+
+
+}
+int main()
+{
+	string a,b;
+	cin>>a>>b;
+
+	int n=a.size();
+	int m=b.size();
+
+	
+
+	memset(dp,0,sizeof(dp));
+
+    //construct the lcs matrix
+	for(int i=1;i<=n;i++)
+	{
+		for(int j=1;j<=m;j++)
+		{
+			if(a[i-1]==b[j-1])
+				dp[i][j]=dp[i-1][j-1]+1;
+			else
+				dp[i][j]=max(dp[i-1][j],dp[i][j-1]);
+		}
+	}
+
+   set<string> ans=getAllLCS(a,b,n,m);
+
+   for(auto it:ans)
+   cout<<it<<" ";	
+}

Greedy Algorithms/Huffman_Encoding/huffman_encoding.c++

@@ -0,0 +1,83 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+//leaf node contains character(data), intermediate nodes contains frequency
+struct node
+{
+    struct node *l;
+    struct node *r;
+    char data; 
+    int freq;
+};
+
+struct compare{
+    bool operator()(struct node *n1,struct node *n2)
+    {
+         return n1->freq>n2->freq;
+    }
+};
+
+void traverse(node *root,string str)
+{
+    if(!root)
+    return ;
+ 
+    if(root->data!='#'){
+     cout<<str<<" ";
+     return;}    
+
+    //append 0 if traverse to left branch of the node otherwise append 1 
+    
+    // if(root->l)
+    traverse(root->l,str+"0");
+    //if(root->r)
+    traverse(root->r,str+"1");
+}
+int main() {
+	//code
+	
+	int t; //for number of test cases
+	cin>>t;
+	while(t--)
+	{
+	    string s;
+	    cin>>s;
+	    priority_queue<node*,vector<node*>,compare> pq;//minheap;
+	    
+	    
+	    int x;
+	    for(int i=0;i<s.length();i++)
+	    {
+	        struct node *nn=(struct node *)malloc(sizeof(struct node));
+	        cin>>x;
+	        nn->freq=x;
+	        nn->data=s[i];
+	        nn->l=nn->r=NULL;
+	        pq.push(nn);
+	    }
+	    
+	   while(pq.size()!=1)
+	    {
+	        struct node *left=pq.top();
+	        pq.pop();
+	        
+	        struct node *right=pq.top();
+	        pq.pop();
+	        
+            node *heapNode=(node*)malloc(sizeof(node));
+            heapNode->data='#'; //  '#'' acts as character in intermediate nodes 
+            heapNode->freq=left->freq+right->freq;
+            heapNode->l=left;
+            heapNode->r=right;
+            
+            pq.push(heapNode);
+	    }
+	    
+	    struct node *root=pq.top();
+	        string ans="";
+	        traverse(root,ans);
+	        cout<<endl;
+	        
+	}
+	return 0;
+}