題目連接html
The string "PAYPALISHIRING"
is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)數組
P A H N A P L S I I G Y I R
And then read line by line: "PAHNAPLSIIGYIR"
this
Write the code that will take a string and make this conversion given a number of rows:code
string convert(string text, int nRows);
convert("PAYPALISHIRING", 3)
should return "PAHNAPLSIIGYIR"
.htm
題目的意思是把字符串上下上下走之字形狀,而後按行輸出,好比包含數字0~22的字符串, 給定行數爲5,走之字形以下:blog
如今要按行輸出字符,即:0 8 16 1 7 9 15 17 2…….ip
若是把以上的數字字符看作是字符在原數組的下標, 給定行數爲n = 5, 能夠發現如下規律:leetcode
(1)第一行和最後一行下標間隔都是interval = n*2-2 = 8 ; 本文地址字符串
(2)中間行的間隔是週期性的,第i行的間隔是: interval–2*i, 2*i, interval–2*i, 2*i, interval–2*i, 2*i, …get
代碼以下,時間複雜度爲O(n),n是字符串的長度:
class Solution { public: string convert(string s, int nRows) { if(nRows == 1)return s; int len = s.size(), k = 0, interval = (nRows<<1)-2; string res(len, ' '); for(int j = 0; j < len ; j += interval)//處理第一行 res[k++] = s[j]; for(int i = 1; i < nRows-1; i++)//處理中間行 { int inter = (i<<1); for(int j = i; j < len; j += inter) { res[k++] = s[j]; inter = interval - inter; } } for(int j = nRows-1; j < len ; j += interval)//處理最後一行 res[k++] = s[j]; return res; } };
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