下列关于使用枚举算法查找整型数组最大值的Python代码片段中，实现正确的是哪一项？

def find_max(arr):
    max_val = 0
    for num in arr:
        if num > max_val:
            max_val = num
    return max_val

def find_max(arr):
    max_val = arr[0]
    for i in range(1, len(arr)):
        if arr[i] > max_val:
            max_val = arr[i]
    return max_val

def find_max(arr):
    max_val = arr[0]
    for i in range(len(arr)):
        if arr[i] < max_val:
            max_val = arr[i]
    return max_val

def find_max(arr):
    max_val = arr[-1]
    for i in range(len(arr)-1, 0, -1):
        if arr[i] > max_val:
            max_val = arr[i]
    return max_val