python2和python3的 leetcoed刷题效率对比

474. 一和零
下面这段代码在python2中可以通过，但是在python3中没有通过，所以python2和python3的效率差别在哪里呢？

class Solution(object):
    def findMaxForm(self, strs, m, n):
        prev, curr = [[0]*(n+1) for _ in range(m+1)], [[0]*(n+1) for _ in range(m+1)]
        for i in range(1, len(strs)+1):
            zeroes, ones = strs[i-1].count('0'), strs[i-1].count('1')
            for j in range(m+1):
                for k in range(n+1):
                    curr[j][k] = 0
                    if j >= zeroes and k >= ones:
                        curr[j][k] = max(prev[j][k], 1+prev[j-zeroes][k-ones])
                    else:
                        curr[j][k] = prev[j][k]
            prev, curr = curr, prev
        return prev[m][n]