[LeetCode] Zigzag Conversion

The key challenge to this problem is to make the code clean. This post has shared a nice example, which is rewritten below in C++.

class Solution {
public:
string convert(string s, int numRows) {
vector<string> vs(numRows, "");
int n = s.length(), i = 0;
while (i < n) {
for (int j = 0; j < numRows && i < n; j++)
vs[j].push_back(s[i++]);
for (int j = numRows - 2; j >= 1 && i < n; j--)
vs[j].push_back(s[i++]);
}
string zigzag;
for (string v : vs) zigzag += v;
return zigzag;
}
};