Question

246. Strobogrammatic Number

中文文档

Description

Given a string num which represents an integer, return true _if_ num _is a strobogrammatic number_.

A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down).

 

Example 1:

Input: num = "69"
Output: true

Example 2:

Input: num = "88"
Output: true

Example 3:

Input: num = "962"
Output: false

 

Constraints:

• 1 <= num.length <= 50
• num consists of only digits.
• num does not contain any leading zeros except for zero itself.

Solutions

Solution 1

class Solution:
  def isStrobogrammatic(self, num: str) -> bool:
    d = [0, 1, -1, -1, -1, -1, 9, -1, 8, 6]
    i, j = 0, len(num) - 1
    while i <= j:
      a, b = int(num[i]), int(num[j])
      if d[a] != b:
        return False
      i, j = i + 1, j - 1
    return True

class Solution {
  public boolean isStrobogrammatic(String num) {
    int[] d = new int[] {0, 1, -1, -1, -1, -1, 9, -1, 8, 6};
    for (int i = 0, j = num.length() - 1; i <= j; ++i, --j) {
      int a = num.charAt(i) - '0', b = num.charAt(j) - '0';
      if (d[a] != b) {
        return false;
      }
    }
    return true;
  }
}

class Solution {
public:
  bool isStrobogrammatic(string num) {
    vector<int> d = {0, 1, -1, -1, -1, -1, 9, -1, 8, 6};
    for (int i = 0, j = num.size() - 1; i <= j; ++i, --j) {
      int a = num[i] - '0', b = num[j] - '0';
      if (d[a] != b) {
        return false;
      }
    }
    return true;
  }
};

func isStrobogrammatic(num string) bool {
  d := []int{0, 1, -1, -1, -1, -1, 9, -1, 8, 6}
  for i, j := 0, len(num)-1; i <= j; i, j = i+1, j-1 {
    a, b := int(num[i]-'0'), int(num[j]-'0')
    if d[a] != b {
      return false
    }
  }
  return true
}