1. 题目

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)

P A H N

A P L S I I GY I RAnd then read line by line: "PAHNAPLSIIGYIR"Write the code that will take a string and make this conversion given a number of rows:

string convert(string text, int nRows);

convert("PAYPALISHIRING", 3) should return "PAHNAPLSIIGYIR".

2. 思路

按规则计算每行的下标顺序进行打印即可。

首行和末行可以同质对待，但是会有下标重叠，进行一下特殊处理即可。

3. 代码

耗时：16ms

class Solution {public:    string convert(string s, int numRows) {        int len = s.length();        if (numRows <= 1 || len <= numRows) {            return s;        }        string so;        so.resize(len);        so = "";        int l = numRows * 2 - 2;        for (int ri = 0; ri < numRows; ri++) {            int i = 0;            int last = -1;            while (true) {                int base = i * l;                int p1 = base + ri;                int p2 = base + l - ri ;                if (p1 < len && p1 != last) so += s[p1];                if (p2 < len && p2 != p1) so += s[p2];                i++;                last = p2;                if (p2 >= len) break;            }        }        return so;    }};