Maximum Length of Pair Chain — Python

# Time:  O(nlogn)
# Space: O(1)

class Solution(object):
    def findLongestChain(self, pairs):
        """
        :type pairs: List[List[int]]
        :rtype: int
        """
        pairs.sort(key=lambda x: x[1])
        cnt, i = 0, 0
        for j in xrange(len(pairs)):
            if j == 0 or pairs[i][1] < pairs[j][0]:
                cnt += 1
                i = j
        return cnt