在Python中查找具有恒定差的最长算术子序列的长度
假设我们有一个数字列表nums和另一个值diff,我们必须找到最长算术子序列的长度,其中子序列中任何相邻数字之间的差异与diff相同。
因此,如果输入为nums = [-1,1,4,7,2,10] diff = 3,则输出将为4,因为我们可以选择类似[1,4,7,10]的子序列。
要解决此问题,我们将遵循以下步骤:
- seen:一个空字典,默认值为0,当键不存在时
- mx:0
- 对于nums中的每个x,执行以下操作
- 如果x-diff存在于seen中,则
- seen [x]:= seen [x-diff] +1
- 否则,
- seen [x]:= 1
- mx:mx和seen [x]的最大值
- 如果x-diff存在于seen中,则
- 返回mx
示例
让我们看一下以下实现以更好地理解-
from collections import defaultdict
def solve(nums, diff):
seen = defaultdict(int)
mx = 0
for x in nums:
if x - diff in seen:
seen[x] = seen[x - diff] + 1
else:
seen[x] = 1
mx = max(mx, seen[x])
return mx
nums = [-1, 1, 4, 7, 2, 10]
diff = 3
print(solve(nums, diff))
输入
[-1, 1, 4, 7, 2, 10],3
输出
4