Description

Submission

class Solution {
public:
    string convert(string s, int numRows) {
        int n = s.length();
        vector<string> grid(numRows);

        int x = 0, dir = 1;

        for(int i = 0; i < n; ++i) {
            grid[x].push_back(s[i]);
            if(numRows > 1) x += dir;

            if(x == numRows - 1 || x == 0) {
                dir = -dir;
            }
        }
        
        string ret;
        for(auto& s: grid) {
            ret += s;
        } 

        return ret;
    }
};

// down:       1,0
// upper right: -1, 1
// down:      1, 0