python數據結構與算法：二分查找

二分查找：python 實現

def binary_seaech(alist,item):
    """二分查找  遞歸實現"""
    n = len(alist)
    if n > 0:
        mid = n // 2
        if alist[mid] == item:
            return True
        elif item < alist[mid]:
            return binary_seaech(alist[:mid],item)
        else:
            return binary_seaech(alist[mid+1:],item)
    return False

def binary_find(alist, item):
    """二分查找  非遞歸實現"""
    n = len(alist)
    first = 0
    last = n-1
    while first <= last:
        mid = (first + last) // 2
        if alist[mid] == item:
            return True
        elif item < alist[mid]:
            last = mid-1

        else:
            first = mid + 1
    return False

if __name__ == "__main__":
    li = [17, 21, 3, 4 ,5 ,55, 77 ,93]
    print(binary_find(li,5))
    print(binary_find(li,200))