. - 力扣（LeetCode）

class Solution {
public:string convert(string s, int numRows) {int n = s.length(), r = numRows;if (r == 1 || r >= n) {return s;}int t = r * 2 - 2;int c = (n + t - 1) / t * (r - 1);vector<string> mat(r, string(c, 0));for (int i = 0, x = 0, y = 0; i < n; ++i) {mat[x][y] = s[i];if (i % t < r - 1) {++x; // 向下移动} else {--x;++y; // 向右上移动}}string ans;for (auto &row : mat) {for (char ch : row) {if (ch) {ans += ch;}}}return ans;}
};