Leetcode diary: 6. Zigzag Conversion

P   A   H   NA P L S I I GY   I   R

what I notice is that     1.) start at 0,     2.) whenever starting at 0, we put in one letter into each row    3.) after that we are at currentRow = numRows-1;    4.) next we are at numRows-2;    5.) we then only put a letter for row == numRows-2, all else is ""    6.) we then decrement currentRow and repeat #5 until currentRow == 0     7.) we repeat 1 to 6 until all letters are used.    we can then loop through the matrix and get the concatenated string    we don't need a 2d array, we can just use array of strings

var convert = function(s, numRows) {        let currentRow = 0;     let currentSIndex = 0;    let upwardIndex = numRows-1;    const matrix = new Array(numRows).fill("");    while (currentSIndex < s.length) {        while(currentRow < numRows && currentSIndex < s.length) {            matrix[currentRow++] += s[currentSIndex++]        }        currentRow--                    //cause currentRow === numRows at this point;        if(numRows >= 2) currentRow--;  //All start at numRows-2 except if numRows === 1        while(currentRow > 0) {            upwardIndex = numRows-1;            while(upwardIndex >-1 && currentSIndex < s.length) {                if(upwardIndex === currentRow) {                    matrix[upwardIndex] += s[currentSIndex++];                }                 upwardIndex--            }            currentRow--;        }    }    return matrix.join("")};