Here is the implementation for Decode Ways (LeetCode ). Time: , Space: or with space reduction. The DP is simple. The tricky part is handling the edge cases correctly. The implementation follows directly from the recurrence. Each line of code corresponds to part of the mathematical formula. Walk through a small example step by step to verify your understanding. Trace through a short string like "" to see how the DP table fills.
Time complexity: .
Space complexity: .