Total Accepted: 10689
Total Submissions: 30073
Difficulty: Medium
A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down).
Find all strobogrammatic numbers that are of length = n.
For example,Given n = 2, return ["11","69","88","96"]
.
Hint:
Try to use recursion and notice that it should recurse with n - 2 instead of n - 1.
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(E) Strobogrammatic Number (H) Strobogrammatic Number III
public class Solution {
// https://discuss.leetcode.com/topic/20753/ac-clean-java-solution
public List<String> findStrobogrammatic(int n) {
return helper(n, n);
}
private List<String> helper(int n, int m) {
if (n == 0) return new ArrayList<String>(Arrays.asList(""));
if (n == 1) return new ArrayList<String>(Arrays.asList("0", "1", "8"));
List<String> list = helper(n - 2, m);
List<String> res = new ArrayList<String>();
for (int i = 0; i < list.size(); i++) {
String s = list.get(i);
if (n != m) res.add("0" + s + "0");
res.add("1" + s + "1");
res.add("6" + s + "9");
res.add("8" + s + "8");
res.add("9" + s + "6");
}
return res;
}
}
