ZigZag Conversion

Problem

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

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

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

Input: s = "A", numRows = 1
Output: "A"

Solution

使用一个二维数组，存储每行结果。

var convert = function (s, numRows) {
    if (numRows === 1) return s;
    const conversionArr = [];
    for (let i = 0; i < numRows; i++) {
        conversionArr.push([]);
    }
    for (let i = 0; i < s.length; i++) {
        const quotient = parseInt(i / (numRows - 1));
        const remainder = i % (numRows - 1);
        if (quotient % 2 !== 0) {
            conversionArr[numRows - remainder - 1].push(s[i]);
        } else {
            conversionArr[remainder].push(s[i]);
        }
    }
    let res = "";
    for (let i = 0; i < conversionArr.length; i++) {
        for (let ii = 0; ii < conversionArr[i].length; ii++) {
            res += conversionArr[i][ii];
        }
    }
    return res;
};

另一种方式

var convert = function (s, numRows) {
    if (numRows === 1) return s;

    const rows = [];
    for (let i = 0; i < numRows; i++) {
        rows.push("");
    }

    var curRow = 0;
    var goingDown = false;
    for (let i = 0; i < s.length; i++) {
        rows[curRow] += s[i];

        if (curRow === 0 || curRow === numRows - 1) goingDown = !goingDown;

        curRow += goingDown ? 1 : -1;
    }

    let res = "";
    for (let i = 0; i < rows.length; i++) {
        res += rows[i];
    }

    return res;
};