Sword finger offer II 035 Minimum time difference

The finger of the sword Offer II 035. Minimum time difference

def getMinutes(t:str)->int:
        return ((ord(t[0])-ord('0'))*10+ord(t[1])-ord('0'))*60+(ord(t[3])-ord('0'))*10+ord(t[4])-ord('0') 
class Solution:
    def findMinDifference(self, timePoints: List[str]) -> int:
        n=len(timePoints)
        if n>1440: return 0
        timePoints.sort()
        ans=float('inf')
        t0Minutes=getMinutes(timePoints[0])
        preMinutes=t0Minutes
        for i in range (1,n):
            curMinutes=getMinutes(timePoints[i])
            ans=min(ans,curMinutes-preMinutes)
            preMinutes=curMinutes
        ans=min(ans,t0Minutes+1440-curMinutes)
        return ans