179. Largest Number

题目

题目来自leetcode

Given a list of non negative integers, arrange them such that they form the largest number.

For example, given [3, 30, 34, 5, 9], the largest formed number is 9534330.

Note: The result may be very large, so you need to return a string instead of an integer.

思路

一个特殊的排序问题，解决方法如下，同样，java中也可以按这个思路来写

python代码

class Solution:
    # @param num, a list of integers
    # @return a string
    def largestNumber(self, num):
        if len(num) == 0:
            return
        for i in xrange(len(num)):
            num[i] = str(num[i])

        num.sort(reverse = True,cmp=self.sortbystr)
        rs = ""
        print num
        for i in num:
            rs += i

        return rs if int(rs) != 0 else "0"

    def sortbystr(self,a,b):
        if a == b:
           return 0
        return 1 if str(a)+str(b) > str(b) + str(a) else -1