1871. Jump Game VII

Problem Link

Description

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You are given a 0-indexed binary string s and two integers minJump and maxJump. In the beginning, you are standing at index 0, which is equal to '0'. You can move from index i to index j if the following conditions are fulfilled:

• i + minJump <= j <= min(i + maxJump, s.length - 1), and
• s[j] == '0'.

Return true if you can reach index s.length - 1 in s, or false otherwise.

 

Example 1:

Input: s = "011010", minJump = 2, maxJump = 3
Output: true
Explanation:
In the first step, move from index 0 to index 3. 
In the second step, move from index 3 to index 5.

Example 2:

Input: s = "01101110", minJump = 2, maxJump = 3
Output: false

 

Constraints:

• 2 <= s.length <= 105
• s[i] is either '0' or '1'.
• s[0] == '0'
• 1 <= minJump <= maxJump < s.length

Solution

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Python3

class Solution:
    def canReach(self, s: str, minJump: int, maxJump: int) -> bool:
        dp = [c == "0" for c in s]
        m = 0
        
        for i in range(1, len(s)):
            if i >= minJump: m += dp[i - minJump]
            if i > maxJump: m -= dp[i - maxJump - 1]
            
            dp[i] &= m > 0
        
        return dp[-1]