字符串z字变换

题目描述 (字符串z字变换 leetcode上的题目)

	将字符串 "PAYPALISHIRING" 以Z字形排列成给定的行数：
	P   A   H   N
	A P L S I I G
	Y   I   R
	之后从左往右，逐行读取字符："PAHNAPLSIIGYIR"
	
	实现一个将字符串进行指定行数变换的函数:
	
	string convert(string s, int numRows);
	示例 1:
	
	输入: s = "PAYPALISHIRING", numRows = 3
	输出: "PAHNAPLSIIGYIR"
	示例 2:
	
	输入: s = "PAYPALISHIRING", numRows = 4
	输出: "PINALSIGYAHRPI"
	解释:
	P     I    N
	A   L S  I G
	Y A   H R
	P     I

解题思路(本题 我的思路时间复杂度太高,没有参考价值.所以这里直接给给出官方的解题思路)

	我们可以使用 \text{min}( \text{numRows}, \text{len}(s))min(numRows,len(s)) 个列表来表示 Z 字形图案中的非空行。
	从左到右迭代 ss，将每个字符添加到合适的行。可以使用当前行和当前方向这两个变量对合适的行进行跟踪.
	只有当我们向上移动到最上面的行或向下移动到最下面的行时，当前方向才会发生改变。

python 实现(官方思路)

class Solution:
    def convert(self, s, numRows):
        """
        :type s: str
        :type numRows: int
        :rtype: str
        """
        index,flag = -1,1
        num_row = min(len(s),numRows)
        # print(num_row)
        list_all=[[] for i in range(num_row)]
        # print(list_all)
        if s is None or len(s)==0:
            return ""
        elif numRows==1:
            return s
        else:
            for i in range(len(s)):
                char = s[i]
                # print(char)
                index = index+flag
                list_all[index].append(char)

                if index == num_row-1:
                    flag = -1
                elif index == 0:
                    flag = 1
        #遍历所有的列表 打印出来
        res_str=""
        for i in range(num_row):
            res_str+="".join(list_all[i])
        return res_str

solution=Solution()
s = "ABC"
numRows = 1
print(solution.convert(s, numRows))

python 实现(我的思路 brueforce,建议不要看 没什么营养,不过是对的)

import  numpy as np
class Solution(object):
    def convert(self, s, numRows):
        """
        :type s: str
        :type numRows: int
        :rtype: str
        """
        if s=="":
            return ""
        len_s=len(s)
        if numRows==1:
            return s

        flag=2*numRows-2
        # print(flag)
        cloum=int((len_s-1)/flag)+1
        # print(cloum)
        if (cloum-1)*flag+numRows-1<(len_s-1):
            cloum =cloum+ (cloum-1)*(numRows-2)+(len_s-1-((cloum-1)*flag+numRows-1))
        else:
            cloum = cloum + (cloum - 1) * (numRows - 2)
        # print(cloum)
        matrix = [["xhm" for i in range(cloum)] for i in range(numRows)]
        # matrix=np.zeros((numRows,cloum))
        j=0
        i=0
        cloum_index=-1
        index=0
        while index<len_s:
            cloum_index+=1
            max_index = cloum_index * flag + numRows - 1
            while index<=max_index  and index<len_s:
                matrix[i][j] = s[index]
                i+=1
                index+=1
            if index<len_s:
                # cloum_index+=1
                # j += 1
                i -= 1
                j += 1
                i -= 1
                while i>=1 and index<len_s:
                    matrix[i][j] = s[index]
                    j += 1
                    i -= 1
                    index+=1
        convert_str=""
        for i in range(numRows):
            convert_str+="".join(matrix[i])
        return convert_str.replace("xhm","")


# PINALSIGYAHRPI
# PINALSIGYAHR
if __name__=='__main__':
    solution=Solution()
    print(solution.convert("wjkakhxhsglmmhstrwgulfztwhhjlbihmviwehfwntibadvubdomiphgxpsiscsexccbjhazakadnvxqanelemtbdlmvoezlgbprkpqlbtqpqphrcmcgyvkbhwyvcxikazbkquxsnpjdeqwicyrcwbfdzdabcklcmmpciouvedbiwxryyidulizkmblonwtzkkcvayqectpariyrqdldmmnynaoawjaivedwcwcgrrgibhbtkmwwyjwnjnohyqsuuxqwvufnmlxnszhfnfbmpabaprknhchdzzaxufkishxngeswkvkbvlbkdlamphqrhsodzylrhieqpymbuwcrhfemtezklpbuhrxgpkzzvgpkedlyzpqiwuvrywelnfguxfcosdpnjexohkoiberzaotymxmzeuvdbzutcjimqhcxrqiuxbwxrpydokcsgxwhwqdazloptqpmjzjgafftwdwkpacxzafxqkxsvmjqeadpbmvbtbupgsbysdvtecqwmqqiecaicdyervhkyebhwcfricmofdmttddxfehjhhnbdxnbbpiztpsdufrzkeudjycqcjzltpmwmczprkqmblqvqjwcnrfypjotuoenftlrvlioxycylsubcqfrhksyvgrqwyfbtruqecgbdibodvshoxaxksyhbrxxrfbkyvccaifftgtwendulfrxyrebjeaajbljzplzyseryzpenuyazszxldyujzvucidbxqcxiiqjifnxbozbiyatdzqpaljevpisfksovkxfqmctcdumdviiwyxwljcgykadvsrsdqxvfbojelwjgercerapacvypxdmqxevpbsucieitctbikdmdfdfkydzvjlngpkvqcsunyeiaxkijnwnvzsfzyewhpkpewmwbeqocwwetgmcwkrrjkwikahtrtivpurqbjgffdkalwcjjuasgydqamjrftmupfnqqtwxyixmgavp",621))