rotated-digits.cpp

/*
 * Copyright (c) 2018 Christopher Friedt
 *
 * SPDX-License-Identifier: MIT
 */

#include <unordered_map>
#include <unordered_set>

using namespace std;

class Solution {
public:
  int rotatedDigits(int N) {

    int total = 0;

    for (int x = 1; x <= N; x++) {
      int xx;
      int digit;
      int y;
      int k;

      for (k = 1, xx = x, digit = xx % 10, y = 0; xx;
           xx /= 10, digit = xx % 10, k *= 10) {
        if (3 == digit || 4 == digit || 7 == digit) {
          goto just_continue;
        }
        if (!(0 == digit || 1 == digit || 8 == digit)) {
          switch (digit) {
          case 2:
            digit = 5;
            break;
          case 5:
            digit = 2;
            break;
          case 6:
            digit = 9;
            break;
          case 9:
            digit = 6;
            break;
          }
        }
        y += k * digit;
      }

      // the number must be changed
      if (x == y) {
        continue;
      }

      total++;

    just_continue:
      continue;
    }

    return total;
  }
};