leetcode/src/s0006_zigzag_conversion.cpp

#include "s0006_zigzag_conversion.hpp"

// 简单地找规律

// n = 3
// 0 4 8 12   2*(n-1) * col
// 1 3 5 ...  (n-1) * col + 1
// 2 6 10     2*(n-1) * col + (n-1)

// n = 4
// 0     6     12   2*(n-1)*col
// 1   5 7   11     2*(n-1)*col+row, 2*(n-1)*col-row
// 2 4   8 10       2*(n-1)*col+row, 2*(n-1)*col-row
// 3     9          2*(n-1)*col + (n-1)

string S0006::convert(string s, int numRows) {
  string r = "";
  int l = s.length();
  if (l == 1 || numRows == 1) {
    return s;
  }
  for (int col = 0; 2 * (numRows - 1) * col < l; col++) {
    r += s[2 * (numRows - 1) * col];
  }
  if (numRows >= 3) {
    for (int row = 1; row < numRows - 1; row++) {
      for (int col = 0;; col++) {
        if (col == 0) {
          if (2 * (numRows - 1) * col + row < l) {
          r += s[2 * (numRows - 1) * col + row];
          }
        } else {
          if (2 * (numRows - 1) * col - row < l) {
            r += s[2 * (numRows - 1) * col - row];
          } else {
            break;
          }
          if (2 * (numRows - 1) * col + row < l) {
            r += s[2 * (numRows - 1) * col + row];
          } else {
            break;
          }
        }
      }
    }
  }
  for (int col = 0; 2 * (numRows - 1) * col + (numRows - 1) < l; col++) {
    r += s[2 * (numRows - 1) * col + (numRows - 1)];
  }
  return r;
}