public class Solution
extends Object
2222 - Number of Ways to Select Buildings\.
Medium
You are given a **0-indexed** binary string `s` which represents the types of buildings along a street where:
* `s[i] = '0'` denotes that the ith building is an office and
* `s[i] = '1'` denotes that the ith building is a restaurant.
As a city official, you would like to **select** 3 buildings for random inspection. However, to ensure variety, **no two consecutive** buildings out of the **selected** buildings can be of the same type.
* For example, given `s = "0**0**1**1**0**1**"`, we cannot select the 1st, 3rd, and 5th buildings as that would form `"0**11**"` which is **not** allowed due to having two consecutive buildings of the same type.
Return _the **number of valid ways** to select 3 buildings._
**Example 1:**
**Input:** s = "001101"
**Output:** 6
**Explanation:** The following sets of indices selected are valid:
- [0,2,4] from "**0**0**1**1**0**1" forms "010"
- [0,3,4] from "**0**01**10**1" forms "010"
- [1,2,4] from "0**01**1**0**1" forms "010"
- [1,3,4] from "0**0**1**10**1" forms "010"
- [2,4,5] from "00**1**1**01**" forms "101"
- [3,4,5] from "001**101**" forms "101"
No other selection is valid. Thus, there are 6 total ways.
**Example 2:**
**Input:** s = "11100"
**Output:** 0
**Explanation:** It can be shown that there are no valid selections.
**Constraints:**
* 3 <= s.length <= 105
* `s[i]` is either `'0'` or `'1'`.