6. Zigzag Conversion

Posted on Edited on In

6. Zigzag Conversion

Description

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)

1
2
3
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:

1
string convert(string s, int numRows);

Example 1:

1
2
Input: s = "PAYPALISHIRING", numRows = 3
Output: "PAHNAPLSIIGYIR"

Example 2:

1
2
3
4
5
6
7
Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"
Explanation:
P     I    N
A   L S  I G
Y A   H R
P     I

Example 3:

1
2
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

Hints/Notes

Solution

Language: C++

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
class Solution {
public:
    string convert(string s, int numRows) {
        if (numRows == 1) {
            return s;
        }
        vector<string> rows(numRows);
        int n = s.size(), curRow = 0, curDir = 1;
        for (int i = 0; i < n; i++) {
            rows[curRow].push_back(s[i]);
            curRow += curDir;
            if (curRow == numRows) {
                curRow = numRows - 2;
                curDir = -1;
            } else if (curRow == -1) {
                curRow = 1;
                curDir = 1;
            }
        }
        string res;
        for (auto& row : rows) {
            res += row;
        }
        return res;
    }
};