外部排序，C++实现

K个排序的数组合并，用到了败者树
相关内容参考了，严蔚敏的《数据结构》

//// Created by Han on 16/5/2.//#include <iostream>#include <cstdio>#include <vector>#include <string>#include <sstream>#include <cstring>#include <fstream>#include <algorithm>using namespace std;const int  MYMAX = 123456789;const int  MYMIN = -123456789;int invalid_count = 0;void Adjust_LoserTree(int s,vector<int>& loser_tree,const vector<int>& input_vals){    int K = loser_tree.size();    int parent = (s+K)/2;//notice    while(parent > 0){        if(input_vals[s] > input_vals[loser_tree[parent]]){ // s为当前胜者            int tmp = s;            s = loser_tree[parent];            loser_tree[parent] = tmp;        }        parent = parent/2;    }    loser_tree[0] = s;}void Build_LoserTree(vector<int>& loser_tree, vector<int>& input_vals){    int K = input_vals.size() -1;    loser_tree.resize(K);    //init    input_vals[K] = MYMIN;    for(size_t i=1;i<K;++i){        loser_tree[i] = K;    }    for(int i=K-1;i>=0;--i){        Adjust_LoserTree(i,loser_tree,input_vals);    }}int get_value(ifstream& i_fstream, bool& if_valid){    int res_val = MYMAX;    int val;    if(if_valid){        if(i_fstream >> val){ //未达到eof            res_val = val;        } else{            if_valid = false;            invalid_count += 1;        }    }    return res_val;}void Merge_KSort(vector<ifstream*> &i_fstreams,ofstream* o_fstream){    size_t K = i_fstreams.size();    bool* valid_streams = new bool[K]();    for(size_t i=0;i<K;++i){        valid_streams[i] = true;    }    vector<int> input_vals;    input_vals.resize(K+1);//facilitate to build loser tree    for(size_t i=0;i<K;++i){        input_vals[i] = get_value(*(i_fstreams[i]),valid_streams[i]);    }    //Build loser tree    vector<int> loser_tree;    Build_LoserTree(loser_tree,input_vals);    //find min and adjust    while(invalid_count < K){        int sel_id = loser_tree[0];        *o_fstream << input_vals[sel_id] << " " << flush;        input_vals[sel_id] = get_value(*(i_fstreams[sel_id]),valid_streams[sel_id]);        Adjust_LoserTree(sel_id,loser_tree,input_vals);    }    //close stream    for(size_t i=0;i<i_fstreams.size();++i){        (*(i_fstreams[i])).close();    }    (*o_fstream).close();}void InterSort(string file_name){    ifstream i_fstream(file_name);    vector<int> vals;    int val;    while(i_fstream >> val){        vals.push_back(val);    }    sort(vals.begin(),vals.end());    i_fstream.close();    ofstream o_fstream(file_name);    for(size_t i=0;i < vals.size();++i){        o_fstream << vals[i] << " " << flush;    }    o_fstream.close();}int main(){    //input files    vector<string> file_names;    string my_dir = "/Users/HAN/Documents/";    file_names.push_back(my_dir + "data1.txt");    file_names.push_back(my_dir + "data2.txt");    file_names.push_back(my_dir + "data3.txt");    size_t K = file_names.size();    //InterSort for every file    for(size_t i=0;i<K;++i){        InterSort(file_names[i]);    }    //input streams    vector<ifstream*> input_streams;    for(size_t i=0;i<K;++i){        ifstream* input_stream = new ifstream(file_names[i]);        input_streams.push_back(input_stream);    }    //output file    string output_file = my_dir +  "data.txt";    ofstream output_stream(output_file);    //merger sort for k input streams to output stream    Merge_KSort(input_streams,&output_stream);}

测试用例：
输入
data1.txt: 3 8 9 7 6
data2.txt: 0 2 6 7 8 1
data3.txt: 0 1 2 5 9 8 7 6

输出
data.txt: 0 0 1 1 2 2 3 5 6 6 6 7 7 7 8 8 8 9 9