[Lintcode]182. Delete Digits

182. Delete Digits

• 本题难度: Medium
• Topic: Greedy

Description

Given string A representative a positive integer which has N digits, remove any k digits of the number, the remaining digits are arranged according to the original order to become a new positive integer.

Find the smallest integer after remove k digits.

N <= 240 and k <= N,

Example
Given an integer A = "178542", k = 4

return a string "12"

我的代码

class Solution:
    """
    @param A: A positive integer which has N digits, A is a string
    @param k: Remove k digits
    @return: A string
    """
    def DeleteDigits(self, A, k):
        while(k>0):
            l = len(A)
            k = k-1
            for i in range(1,l):
                if A[i-1]>A[i]:
                    A = str(int(A[:i-1]+A[i:]))
                    break
                if i == l-1:
                    A = str(int(A[:-1]))
        return A

思路

当删除的元素比后一个与小的时候，不如直接删除最后一个元素。
在删除元素比后一个元素大的情况下，删除前面的元素肯定比删除后面元素带来的利益大。

• 时间复杂度 O(n*k)