ZigZag Conversion

LeetCode #6

Description:

Example:

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".

Idea:

The trick is that every cycle has 2*numRows-2 element, Then just figure out the location of each char

set a vector of string, the first one is the first row, and so on

level= i % (2*numRows - 2);
if(level<numRows){
    subs[level] += s[i];
}
else{
    subs[2*numRows-2-level] += s[i];
}

Code:

class Solution {
public:
// The trick is that every cycle has 2*numRows-2 element, Then just figure out the location of each char
// set a vector of string, the first one is the first row, and so on
    string convert(string s, int numRows) {
        if(numRows==1) return s;

        vector<string> subs(numRows);
        int level;

        for (int i=0; i<s.size(); ++i){
            level= i % (2*numRows - 2);
            if(level<numRows){
                subs[level] += s[i];
            }
            else{
                subs[2*numRows-2-level] += s[i];
            }
        }

        string result;
        for (int i=0; i<numRows; ++i){
            result += subs[i];
        }

        return result;

    }
};