面试经典150题——Day22

一、题目

6. Zigzag Conversion

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 G
Y I R
And 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 s, int numRows);

Example 1:

Input: s = “PAYPALISHIRING”, numRows = 3
Output: “PAHNAPLSIIGYIR”
Example 2:

Input: s = “PAYPALISHIRING”, numRows = 4
Output: “PINALSIGYAHRPI”
Explanation:
P I N
A L S I G
Y A H R
P I
Example 3:

Input: s = “A”, numRows = 1
Output: “A”

Constraints:

1 <= s.length <= 1000
s consists of English letters (lower-case and upper-case), ‘,’ and ‘.’.
1 <= numRows <= 1000

题目来源： leetcode

二、题解

找到字符串的周期规律，构建对应的字符串数组，

class Solution {
public:
    string convert(string s, int numRows) {
        int n = s.length();
        if(numRows == 1) return s;
        int reminder = 2 * numRows - 2;
        vector<string> rowString(numRows,"");
        for(int i = 0;i < n;i++){
            int mod = i % reminder;
            if(mod < numRows - 1) rowString[mod] += s[i];
            else rowString[numRows - 1 - (mod - numRows + 1)] += s[i];
        }
        string res = "";
        for(int i = 0;i < numRows;i++){
            res += rowString[i];
        }
        return res;
    }
};