246. Strobogrammatic Number

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

Write a function to determine if a number is strobogrammatic. The number is represented as a string.

For example, the numbers "69", "88", and "818" are all strobogrammatic.

一刷
two pointer

public class Solution {
    public boolean isStrobogrammatic(String num) {
        int lo = 0, hi = num.length()-1;
        while(lo

二刷
短一点

public class Solution {
    public boolean isStrobogrammatic(String num) {
    String[] stro = {"11", "88", "69", "96", "00"};
    Set dict = new HashSet<>(Arrays.asList(stro));
    for (int i=0, j=num.length()-1; i <= j; i++, j--){
        if(i==j){
            if(num.charAt(i)!='1' && num.charAt(i)!='8' && num.charAt(i)!='0') return false;
        }else{
            if (!dict.contains(num.charAt(i) + "" + num.charAt(j)))
            return false;
        }
    }
    return true;
}
}