Number of Ways to Select Buildings
You are given a 0-indexed binary string s which represents the types of buildings along a street where: As a city official, you would like to select 3 buildings for random...
You are given a 0-indexed binary string s which represents the types of buildings along a street where:
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.
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 "001101" forms "010" - [0,3,4] from "001101" forms "010" - [1,2,4] from "001101" forms "010" - [1,3,4] from "001101" forms "010" - [2,4,5] from "001101" forms "10^1" - [3,4,5] from "001101" forms "10^1" 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 <= 10^5
- s[i] is either '0' or '1'.
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