C++写geohash

http://www.cnblogs.com/LBSer/p/3310455.html

http://www.sxrczx.com/pages/my.oschina.net/853294317/blog/296594.html

http://community.apicloud.com/bbs/forum.php?mod=viewthread&tid=5300

受朋友委托写个查找附近人的算法，当然是不会写，不知道从何下手，于是学习了下geohash算法。看懂后开始一步步实现，当然还没有完全写完。不会之处在于：如何对已有的字符串进行前缀匹配的呢？怎么查找附近的人呢？

写了很多注释，怕自己以后看不懂。这也算是第一次体会到算法在工程中的作用。想起以前老师说算法在开发中没用！！表示汗颜、无语。

#include<iostream>
#include<stdio.h>
#include<string>
#include<string.h>
#include<map>
#include <stdlib.h>
#include <stdio.h>
#include <winsock.h>
#include <mysql.h>
#include <cstring>
using namespace std;
map<string, string> base32;

//将纬度、经度二进制化
//纬度范围(-90, 90)
//经度范围(-180, 180)
//传入w,返回二进制编码
//max_step控制递归次数同时也是二进制编码长度
//注意返回的是逆序的字符串 max_step必须是5的倍数
string geohash_w_bin(double w,double left,double right,int step,int max_step) 
{
    if (step > max_step) 
    {
        return "";
    }
    double mid = (left + right)*1.0 / 2;

    if (w >= left && w <= mid) {
        return geohash_w_bin(w, left, mid,step+1,max_step)+"0"; 
    }
    if (w >= mid && w <= right) {
        return geohash_w_bin(w, mid, right,step+1,max_step)+"1";
    }

}

//合并经纬度
//传入经度和纬度 返回合并的二进制编码
string geohash_merge(string j, string w) {
    string s;
    for (int i = 0; i <j.size(); i++){
        s += j[i];
        s += w[i];
    }
    return s;
}

//二进制编码base32化
string geohash_base32(string s) {
    string temp;
    string ans;
    for (int i = 0; i < s.size(); i++) {
        temp += s[i];
        if ((i + 1) % 5 == 0) {
            ans+=base32[temp];
            temp = "";
        }
    }

    return ans;
}

//*****************
//将经纬度转为base32 返回base32编码
//w为纬度 j为经度 
//*****************
string geohash(double j, double w) {
    string s_w="", s_j="";
    string s="", ss="";
    
    s_w = geohash_w_bin(w, -90, 90, 1, 30);
    s_j = geohash_w_bin(j, -180, 180, 1, 30);
    
    reverse(s_w.begin(), s_w.end());
    reverse(s_j.begin(), s_j.end());

    s = geohash_merge(s_j, s_w);
    s= geohash_base32(s);
    return s;
}

//有返回值的数据库写入
MYSQL_RES * executeQuery(char *sql)
{
    MYSQL* pConn = mysql_init(0);
    if (!mysql_real_connect(pConn, "localhost", "root", "root", "study1", 0, 0, 0))
    {
        goto error;
    }
    if (mysql_query(pConn, "set names gbk"))
    {
        goto error;
    }
    if (mysql_query(pConn, sql))
    {
        goto error;
    }
    
        MYSQL_RES *result = mysql_store_result(pConn);
        mysql_close(pConn);
        return result;
    
error:
        cout << "执行出错 " << mysql_error(pConn)<<endl;
    //fprintf(cgiOut, "执行出错 %s", mysql_error(pConn));
    //printf("执行出错 %s",mysql_error(pConn));
exit:
    mysql_close(pConn);
}

//无返回值的数据库写入
void executeNonQuery(char * sql)
{
    MYSQL* pConn = mysql_init(0);
    if (!mysql_real_connect(pConn, "localhost", "root", "root", "study1", 0, 0, 0))
    {
        goto error;
    }
    if (mysql_query(pConn, "set names gbk"))
    {
        goto error;
    }
    if (mysql_query(pConn, sql))
    {
        goto error;
    }
    goto exit;
error:
    cout << "执行出错 " << mysql_error(pConn) << endl;
    /*cgiHeaderContentType("text/html;charset=gbk");
    fprintf(cgiOut, "执行出错 %s", mysql_error(pConn));*/
    //printf("执行出错 %s",mysql_error(pConn));
exit:
    mysql_close(pConn);
}


//字符串截取函数
string jiequ(string s, int l, int r) {
    string temp;
    for (int i = 0; i < r; i++)
    {
        temp += s[i];
    }
    return temp;
}


//输入base32编码，结果打印在屏幕上
//查询编码前缀相同的
void geohash_search(string base32)
{
    for (int i = base32.size()-3; i > 0; i--)
    {
        string temp_base32 = jiequ(base32, 0, i);
        const char *temp_c_base32 = temp_base32.c_str();
        char sql[1024]; char *c = "%";
        int f = 0;
        
        sprintf(sql, "select * from t_theatre where base32 like '%s%s'", temp_c_base32,c);
        MYSQL_RES *result = executeQuery(sql);
        MYSQL_ROW row;

        while (row = mysql_fetch_row(result))
        {
            char *base32 = row[1];
            char *name = row[2];
            cout << base32 << " " << name << endl;
            //f = 1;
        }

        /*if (f) {
            return;
        }*/

    }


    

}
int main()
{
    base32["00000"] = "0";
    base32["00001"] = "1";

    base32["00010"] = "2";
    base32["00011"] = "3";

    base32["00100"] = "4";
    base32["00101"] = "5";
    base32["00110"] = "6";
    base32["00111"] = "7";

    base32["01000"] = "8";
    base32["01001"] = "9";
    base32["01010"] = "b";//10
    base32["01011"] = "c";//11
    base32["01100"] = "d";//12
    base32["01101"] = "e";//13
    base32["01110"] = "f";//14
    base32["01111"] = "g";//15

    base32["10000"] = "h";//16
    base32["10001"] = "j";//17
    base32["10010"] = "k";//18
    base32["10011"] = "m";//19
    base32["10100"] = "n";//20
    base32["10101"] = "p";//21
    base32["10110"] = "q";//22
    base32["10111"] = "r";//23
    base32["11000"] = "s";//24
    base32["11001"] = "t";//25
    base32["11010"] = "u";//26
    base32["11011"] = "v";//27
    base32["11100"] = "w";//28
    base32["11101"] = "x";//29
    base32["11110"] = "y";//30
    base32["11111"] = "z";//31

    geohash_search("wttf1y0ewmt3");

    //select * from where like'wttc%'
    //geohash_search("select * from t_theatre where base32 like 'wttc%'");
    

    
    /*while (1) {
        double w, j; char name[128], sql[1024];
        cin >> j >> w>>name;
        
        string base32=geohash(j,w);
        const char *ch = base32.c_str();

        sprintf(sql, "insert into t_theatre(base32,name) values('%s','%s')", ch,name);
        executeNonQuery(sql);
    }*/


    ////insert into t_theatre(base32) values()
    //char sql[] = "insert into t_theatre(base32) values('klkl')";
    //executeNonQuery(sql);
    //120.677252 31.316891
    //cout << geohash(120.677252, 31.316891) << " 精品酒店" << endl;
    //cout << geohash(120.674144, 31.316012) << " 星海实验中学" << endl;
    //    cout<< geohash(120.648933, 31.374867) << " 相称去政府" <<endl;
    //cout << geohash(120.683958, 31.391834) << " 我的位置" <<endl;
        
    /*cout<<"111001001100011111101011100011000010110000010001010001000100";*/
    ////double a = 90.0;
    //string s=geohash_w_bin(104.031601, -180, 180, 1,30);
    //reverse(s.begin(), s.end());
    //cout << s<<endl;
    ////cout << "101010111001001000100101101010";
    ////cout << "110010011111101001100000000000";

    getchar();
    return 0;
}

最后希望自己踏实学习算法。一张纸叠n次可以比天高，而n张纸叠在一起就不一定了。