leetcode-algorithms/src/StrobogrammaticNumber.java at master · anishLearnsToCode/leetcode-algorithms · GitHub

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// https://leetcode.com/problems/strobogrammatic-number

// T: O(N)

// S: O(1)

import java.util.HashMap;

import java.util.Map;

// Strobogrammatic digits: 0, 1, 8

// Strobogrammatic interchangeable digits: 6 --> 9, 9 --> 6

public class StrobogrammaticNumber {

private static final Map<Character, Character> STROBOGRAMMATIC_MIRROR = new HashMap<>() {{

put('0', '0');

put('1', '1');

put('6', '9');

put('8', '8');

put('9', '6');

}};

public boolean isStrobogrammatic(String number) {

for (int i = 0 ; i < number.length() ; i++) {

final char digit = number.charAt(i);

if (!STROBOGRAMMATIC_MIRROR.containsKey(digit)

|| STROBOGRAMMATIC_MIRROR.get(digit) != number.charAt(number.length() - 1 - i)

) {

return false;

}

return true;

}

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