C++学习之二分查找

//radn.cc -->生成随机数
#include <iostream>
#include <string>
#include <vector>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <sys/time.h>
#define ERR_EXIT(m)     do {         perror(m);        exit(EXIT_FAILURE);    }while(0)
using namespace std;

//写入文件
void writeIntegerToFile(int fd, int value) 
{
    char text[100] = {0};
    
    snprintf(text, sizeof text, "%d\n", value);
    
    if(write(fd, text, strlen(text)) == -1)
        ERR_EXIT("write");
}

//返回time
double get_time()  // 对运行时间进行封装
{
    struct timeval tm;
    memset(&tm, 0, sizeof tm);
    if(gettimeofday(&tm, NULL) == -1)
        ERR_EXIT("gettimeofday");
    
    double res = 0.0;
    res += tm.tv_sec;
    res += tm.tv_usec / (double)1000000;
    return res; 
}

int main(int argc, const char *argv[])
{
    double startTime = get_time();
    
    const int kSize = 1000000;
    srand(kSize);
    
    int fd = open("largeT.txt", O_CREAT | O_WRONLY | O_TRUNC, 0666);
    if(fd == -1)
        ERR_EXIT("open");


    for(int i = 0; i != kSize; ++i)
    {
        writeIntegerToFile(fd, rand() % kSize); 
    }

    close(fd);

    double endTime = get_time();
    double cost = endTime - startTime;
    cout << "花费时间 " << cost << " s" << endl;
    return 0;
}

//BinarySearch.cc
#include <iostream>
#include <string>
#include <vector>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/time.h>
#include <algorithm> 
using namespace std ;

bool BinarySearch(const vector<int> vec , int val, int min, int  max)
{
    int mid = (min + max )/2  ;
    while( min <= max )
    {
        if(vec[mid] == val )
        {
            return true ;
        }else if( vec[mid] > val )
        {
            max = mid - 1 ;
            mid = (min + max) / 2 ;
        }else
        {
            min = mid + 1 ;
            mid = (min + max ) / 2 ;
        }
    }
    cout << "The val of the num is :" << val << " " << endl ;
    return false ;
}


int main(int argc, const char *argv[])
{
    FILE* fpLarge = fopen("largeT.txt" , "rb") ;
    FILE* fpSmall = fopen("smallT.txt" , "rb") ;
    if(NULL ==fpLarge  || NULL == fpSmall)
    {
        perror("open");
        exit(1);
    }
    vector<int> Larvec ;
    vector<int> Smlvec ;
   // int Ssize = 10000 ;
    int Lsize = 1000000 ;
    
    char buf[128] ;
    

    while(memset(buf , 0, sizeof(buf)) ,fgets(buf ,sizeof(buf) ,fpLarge)!= NULL)
    {
        int tmp = atoi(buf);
        Larvec.push_back(tmp);
    }
    sort( Larvec.begin() , Larvec.end());

    int val ;
    while(memset(buf , 0, sizeof(buf)) ,fgets(buf ,sizeof(buf) ,fpSmall)!= NULL)
    {
        val = atoi(buf);
        Smlvec.push_back(val);
    }
    int cnt = 0  ;//标记未查找成功的个数
    for(vector<int>::size_type ix = 0 ; ix != Smlvec.size() ; ++ix)
    {
        bool rec ;
        rec = BinarySearch(Larvec , Smlvec[ix], 0 , Lsize );
        if(!rec)
            cnt ++ ;
    }
    cout << "The cnt of Searching false is :  " << cnt << endl ;//输出查找失败总数
    cout << "Time used =  "  << (double)clock()/CLOCKS_PER_SEC << endl ;//输出程序运行时间
    fclose(fpLarge);
    fclose(fpSmall);
    return 0;
}