基础算法——二分查找

二分查找，更新指针：

def binary_search(array, key):
    left = 0
    right = len(array) - 1
    while left <= right:
        mid = left + (right - left) // 2
        if array[mid] == key:
            return mid
        elif array[mid] < key:
            left = mid + 1
        else:
            right = mid - 1

    return -1


arr = [4, 3, 1, 7, 8]
key = 3
arr = sorted(arr)
ans = binary_search(arr, key)
print(ans)

二分查找，递归：

def binary_search(array, left, right, key):                
    mid = left + (right - left) // 2                       
    if array[mid] == key:                                  
        return mid                                         
    elif array[mid] < key:                                 
        return binary_search(array, mid + 1, right, key)   
    elif array[mid] > key:                                 
        return binary_search(array, left, mid - 1, key)    

    return -1                                              


arr = [4, 3, 1, 7, 8]                                      
key = 3                                                    
arr = sorted(arr)                                          
ans = binary_search(arr, 0, len(arr) - 1, key)             
print(ans)