二分查找算法

#include

#include

#include

#include

#include // Include function: Log() 以e为底

const int N = 1001; // 数组元素数目

float count=0.0;

float RowCount=0.0;

using namespace std;

// 声明二分查找算法

int binarySearch( const int b[], int searchKey, int low, int high );

int main() {

int array[N];

int SearchTimes = 10; // SearchTimes: 重复查找每个数组次数

srand(time(0)); // 随机数发生器的初始化函数,使每次产生的随机数不同

cout << "Every array repeat search times: " << SearchTimes << endl;

cout << "Number of Elements" << setw(18) << "理论平均查找次数" << setw(22) << "实际平均查找次数" << endl;

for ( int j=100; j <=1000; j+=100 ) {

array[0]=10+rand()%15;

for(int i=1; i

// 生成递增随机数列

array[i]=array[i-1]+1+rand()%3+rand()%10;

}

// SearchTimes: 重复查找每个数组次数

// C 语言是大小写敏感的

for (int time=0; time < SearchTimes; time++) {

// suffix 为要搜索的元素下标

int suffix = rand() % j;

// key 为要查找的数据

int key = array[suffix];

int result = binarySearch( array, key, 0, j-1 );

}

count = (RowCount / SearchTimes );

RowCount = 0.0;

// 输出

// Function log() 默认以E为底so 用换底公式搞定

cout << setw(18) << j << setw(18) << int( log(j)/log(2) ) + 1.0/2 << setw(22) << count << endl;

count=0.0; // 令全局变量为0

}

return 0;

}

///////////////////////////////////////////////////////////////////////////

// BinarySearch

int binarySearch( const int b[], int searchKey, int low, int high ) {

int middle;

while( low <= high ) {

middle = ( low + high ) / 2;

if (searchKey == b[middle]) {

RowCount++;

return middle;

}

else if ( searchKey < b[middle] ) {

high = middle - 1;

RowCount++;

}

else {

low = middle + 1;

RowCount++;

}

}

return -1; // not found

}