代码拉取完成,页面将自动刷新
同步操作将从 doocs/leetcode 强制同步,此操作会覆盖自 Fork 仓库以来所做的任何修改,且无法恢复!!!
确定后同步将在后台操作,完成时将刷新页面,请耐心等待。
We are given S
, a length n
string of characters from the set {'D', 'I'}
. (These letters stand for "decreasing" and "increasing".)
A valid permutation is a permutation P[0], P[1], ..., P[n]
of integers {0, 1, ..., n}
, such that for all i
:
S[i] == 'D'
, then P[i] > P[i+1]
, and;S[i] == 'I'
, then P[i] < P[i+1]
.How many valid permutations are there? Since the answer may be large, return your answer modulo 10^9 + 7
.
Example 1:
Input: "DID" Output: 5 Explanation: The 5 valid permutations of (0, 1, 2, 3) are: (1, 0, 3, 2) (2, 0, 3, 1) (2, 1, 3, 0) (3, 0, 2, 1) (3, 1, 2, 0)
Note:
1 <= S.length <= 200
S
consists only of characters from the set {'D', 'I'}
.
此处可能存在不合适展示的内容,页面不予展示。您可通过相关编辑功能自查并修改。
如您确认内容无涉及 不当用语 / 纯广告导流 / 暴力 / 低俗色情 / 侵权 / 盗版 / 虚假 / 无价值内容或违法国家有关法律法规的内容,可点击提交进行申诉,我们将尽快为您处理。