# zigzag conversion leetcode

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).

Here is the solution using nested while loop:

```var convert = function(s, numRows) {
if (numRows < 2) {
return s;
}
var matrix = [];
for (var i = 0; i < numRows; i++) {
matrix.push([]);
}
var k = 0;
var i = 0;
var res = '';
while (k < s.length) {
while(i < matrix.length && k < s.length) {
matrix[i].push(s[k]);  // down
i++;
k++;
}
i = i-2;
while (i >= 0 && k < s.length) {
matrix[i].push(s[k]) // up
i--;
k++;
}
i = i+2;
}
for (var i = 0; i < matrix.length; i++) {
for (var k = 0; k < matrix[i].length; k++) {
res += matrix[i][k];
}
}

```

Here is the solution mix while with for loop:

```var convert = function(s, numRows) {
var len = s.length;
var matrix = [];

var matrix = [];
for (var i = 0; i < numRows; i++) {
matrix.push([]);
}

var i = 0, res='';
while(i < len) {
for(var idx = 0; idx < numRows && i < len; idx++) { // down
matrix[idx].push(s[i]);// add it to the matrix
i++; // then increase
}
for(var idx = numRows - 2; idx >=1 && i< len; idx--){ //up
matrix[idx].push(s[i++]); // another simple way and add the item then increase i
}
}

for(var i = 0; i < matrix.length; i++){
for(var j=0; j< matrix[i].length; j++){
res += matrix[i][j];
}
}

return res;
}
```