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 text, int nRows);
convert(“PAYPALISHIRING”, 3) should return "PAHNAPLSIIGYIR".
Solution 1: Direct Calculation
This solution follows direct definition of the question, when we align the string in ZigZag format:
first and last line: char distance is 2 x numRows - 2
rest lines: char distance is 2 x numRows - 2 - 2 x i
Simply Calculate the result string char position will do
Complexity: O(n)
Code:
string convert(string s, int numRows) {
if(numRows==1 || s.empty()) return s;
string res = "";
int distance = 2 * numRows-2;
for(int i = 0; i < numRows; ++i)
{
int dis = distance - 2*i;
int init = i;
while(init < s.length())
{
res.push_back(s[init]);
if(i==0||i==numRows-1) init += distance;
else{
init+=dis;
dis = distance - dis;
}
}
}
return res;
}