An algorithm for Huffman coding

An algorithm for Huffman coding

Refer to the book "Data structure (c language Edition)" published by Tsinghua University Press and implemented in Java

//Data structureClass huffmannode{ Public intWeight//Weight     Public intParent,lchild,rchild;//parent node, child node subscript position in array     Public Huffmannode(intWeightintParentintLchild,intRchild) { This. Weight = weight; This. parent = parent; This. lchild = Lchild; This. rchild = Rchild; }}/** * @param str_weight_arr array of stored word Fu Quan values * @param number of n characters * @return Calculated Huffman encoding * */     PublicStringhuffmancoding(int[] Str_weight_arr,intN) {if(n<1|| Str_weight_arr.length <n)return NULL;//The number of nodes of the Huffman tree to be constructed is twice times minus 1 of the number of leaf nodes        intNode_num = n2-1;//Create Huffman tree node, array size is node_num+1, we start with subscript 1huffmannode[] Huffmantree =Newhuffmannode[node_num+1];//Put the value in Str_weight_arr into the first n nodes, the first n elements are the leaf nodes of the Huffman tree        The remaining elements are the locations of non-leaf nodes, the ones we need to dynamically add below         for(intI=1; i<=n;i++) Huffmantree[i] =NewHuffmannode (Str_weight_arr[i],0,0,0);//Initialize the remaining elements         for(inti=n+1; i<=node_num;i++) Huffmantree[i] =NewHuffmannode (0,0,0,0);//Establish a Huffman tree, starting with the element labeled N+1, and building the subtree one by one. I's child nodes are the least weighted from 1 to i-1.        //Two nodes, when the traversal is finished, the element labeled Node_num is the root node of the Huffman tree         for(inti=n+1; i<=node_num;i++) {//In the Huffmantree between 1 and i-1 to find the lowest weight and no parent node of the two elements subscript            int[] Child_arr = Selectmintwo (Huffmantree,1, I-1);//Judging under Child_arr non-null            if(Child_arr = =NULL)return NULL;//Constructs a new subtree, the root node subscript is I, the left and right sub-tree position is child_arr[0],child_arr[1]Huffmantree[i].lchild = child_arr[0]; Huffmantree[i].rchild = child_arr[1]; Huffmantree[i].weight = huffmantree[child_arr[0]].weight +huffmantree[child_arr[1]].weight; huffmantree[child_arr[0]].parent = i; huffmantree[child_arr[1]].parent = i; }//end for        //At this point, the weight of these non-leaf nodes increases gradually from the position of subscript n+1 to Node_num.         ///next to generate Huffman encodingstring[] Huffmancode =Newstring[n+1];all elements in the//code_temp array are the Huffman encoding of a letter        Char[] Code_temp =New Char[n];//Huffmancode full, subscript starting from 1         for(intI=1; i<=n;i++) {intStart = n1;//What we require is the Huffman encoding of the given string, and the method passes in an array of weights corresponding to the character one by one in the string            //So, in order, start with each node, and look up until you find a node with 0 and 1 to record the path of the period            //From the leaf to the root of the reverse coding f==0 when the root node has been found             for(intC=1, f=huffmantree[i].parent;f!=0; c=f,f=huffmantree[f].parent) {The node of the//c position is not the left subtree of the F-position node, which is the right subtree of the F-position node, without running .                if(Huffmantree[f].lchild = = c) Code_temp[--start] =' 0 ';ElseCode_temp[--start] =' 1 '; }//The Huffman Code of the I-character is found, the first position of the code_temp array is truncated to the last character            //Assign value to Huffmancode[i]Huffmancode[i] = string.copyvalueof (code_temp, start, Code_temp.length-start); The String result =""; for(String s:huffmancode) result+=s;returnResult }Private int[]Selectmintwo(huffmannode[] Huffmantree,intBeginintEnd) {if(begin<1|| End >huffmantree.length)return NULL;intMAX1 = begin;intMAX2 = begin;intMax_weight = Huffmantree[begin].weight;//Find the lowest weight of the element where the subscript         for(inti=begin;i<=end;i++) {if(huffmantree[i].weight<max_weight && Huffmantree[i].parent = =0) Max1 = i; }//Looking for the second small weight of the element where the subscript         for(inti=begin;i<=end;i++) {if(huffmantree[i].weight<max_weight && Huffmantree[i].parent = =0&& max1! = max2) Max2 = i; }return New int[]{max1,max2}; }}

An algorithm for Huffman coding