Given a string and number of rows ‘n’. Print the string formed by concatenating n rows when input string is written in row-wise Zig-Zag fashion.
Input: str = "ABCDEFGH" n = 2 Output: "ACEGBDFH" Explanation: Let us write input string in Zig-Zag fashion in 2 rows. A C E G B D F H Now concatenate the two rows and ignore spaces in every row. We get "ACEGBDFH" Input: str = "GEEKSFORGEEKS" n = 3 Output: GSGSEKFREKEOE Explanation: Let us write input string in Zig-Zag fashion in 3 rows. G S G S E K F R E K E O E Now concatenate the two rows and ignore spaces in every row. We get "GSGSEKFREKEOE"
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The idea is to traverse the input string. Every character has to go to one of the rows. One by one add all characters to different rows. Below is algorithm:
1) Create an array of n strings, arr[n] 2) Initialize direction as "down" and row as 0. The direction indicates whether we need to move up or down in rows. 3) Traverse the input string, do following for every character. a) Append current character to string of current row. b) If row number is n-1, then change direction to 'up' c) If row number is 0, then change direction to 'down' d) If direction is 'down', do row++. Else do row--. 4) One by one print all strings of arr.
Below is implementation of above idea.
Time Complexity: O(len) where len is length of input string.
Auxiliary Space: O(len)
Thanks to Gaurav Ahirwar for suggesting above solution.
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