二分查找法

Posted 2020-11-16 darklights

一、

#include <iostream>
#include <cassert>
#include <ctime>

using namespace std;

template<typename T>
int binarySearch(T arr[], int n, T target){
    int l = 0, r = n-1;
    while( l <= r ){
        int mid = l + (r-l)/2;
        if( arr[mid] == target )
            return mid;
        if( arr[mid] > target )
            r = mid - 1;
        else
            l = mid + 1;
    }
    return -1;
}

int main() {
    int n = 1000000;
    int* a = new int[n];
    for( int i = 0 ; i < n ; i ++ )
        a[i] = i;
    clock_t startTime = clock();
    for( int i = 0 ; i < 2*n ; i ++ ){
        int v = binarySearch(a, n, i);
        if( i < n )
            assert( v == i );
        else
            assert( v == -1 );
    }
    clock_t endTime = clock();
    cout << "Binary Search (Without Recursion): " << double(endTime - startTime) / CLOCKS_PER_SEC << " s"<<endl;
    delete[] a;
    return 0;
}

二、