leetcode每日一题:(6)ZigZag Conversion

ZigZag Conversion

Question

• leetcode: ZigZag Conversion| LeetCode OJ

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   NA 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".

题解

可以发现首行和末行的重复周期都是 2∗nRows−2，对于首行和末行之间的行，还会额外重复一次，重复的这一次距离本周期起始字符的距离是 2∗nRows−2−2∗i 。

C++

class Solution {public:    string convert(string s, int nRows) {        if (nRows <= 1 || s.length() == 0)  //nRows=1 按下面会死循环           return s;          string ret = "";        const int len = s.size();        int lag = 2*nRows - 2; //循环周期          for (int i = 0; i < nRows; i++) {              for (int j = i; j < len; j += lag) {                  ret += s[j];                    if (i > 0 && i < nRows-1) {  //非首行和末行时                    int t = j + lag - 2*i;                      if (t < len) {                          ret += s[t];                      }                  }              }          }          return ret;    }};

提交成功