664. Strange Printer

Python

2 Dimension DP

class Solution:
    def strangePrinter(self, s: str) -> int:
        if not s:
            return 0

        n = len(s)

        dp = [[0]*n for _ in range(n)]
        for i in range(n):
            dp[i][i] = 1

        for i in range(n-1, -1, -1):
            for j in range(i+1, n):
                if s[i] == s[j]:
                    dp[i][j] = dp[i][j-1]
                    continue
                dp[i][j] = min(
                    dp[i][cur] + dp[cur+1][j]
                    for cur in range(i, j)
                )

        return dp[0][n-1]