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 / ;

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

 }

 //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 = ; 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 = ; i < s.size(); i++) {
         temp += s[i];
         if ((i + ) %  == ) {
             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, -, , , );
     s_j = geohash_w_bin(j, -, , , );

     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();
     if (!mysql_real_connect(pConn, "localhost", "root", "root", "study1", , , ))
     {
         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();
     if (!mysql_real_connect(pConn, "localhost", "root", "root", "study1", , , ))
     {
         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 = ; 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()-; i > ; i--)
     {
         string temp_base32 = jiequ(base32, , i);
         const char *temp_c_base32 = temp_base32.c_str();
         char sql[]; char *c = "%";
         int f = ;

         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[];
             char *name = row[];
             cout << base32 << " " << name << endl;
             //f = 1;
         }

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

     }

 }
 int main()
 {
     base32[""] = "";
     base32[""] = "";

     base32[""] = "";
     base32[""] = "";

     base32[""] = "";
     base32[""] = "";
     base32[""] = "";
     base32[""] = "";

     base32[""] = "";
     base32[""] = "";
     base32[""] = "b";//
     base32[""] = "c";//
     base32[""] = "d";//
     base32[""] = "e";//
     base32[""] = "f";//
     base32[""] = "g";//

     base32[""] = "h";//
     base32[""] = "j";//
     base32[""] = "k";//
     base32[""] = "m";//
     base32[""] = "n";//
     base32[""] = "p";//
     base32[""] = "q";//
     base32[""] = "r";//
     base32[""] = "s";//
     base32[""] = "t";//
     base32[""] = "u";//
     base32[""] = "v";//
     base32[""] = "w";//
     base32[""] = "x";//
     base32[""] = "y";//
     base32[""] = "z";//

     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 ;
 }

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。