列出字符串数组中所有元组的算法

def find_tuples(arr, length):
    result = []
    backtrack(arr, length, [], 0, result)
    return result

def backtrack(arr, length, curr_tuple, start, result):
    if len(curr_tuple) == length:
        result.append(curr_tuple[:])
        return
    
    for i in range(start, len(arr)):
        curr_tuple.append(arr[i])
        backtrack(arr, length, curr_tuple, i + 1, result)
        curr_tuple.pop()

# 示例用法
arr = ["a", "b", "c", "d"]
length = 2
result = find_tuples(arr, length)
print(result)