Create: 1930-unique-length-3-palindromic

javascript/1930-unique-length-3-palindromic-subsequences.js

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+/**
+ * @param {string} s
+ * @return {number}
+ */
+var countPalindromicSubsequence = function (s) {
+ let count = 0;
+ let chars = new Set(s);
+ for(const char of chars){
+ let first = s.indexOf(char),last = s.lastIndexOf(char);
+ count += new Set(s.slice(first + 1, last)).size;
+ }
+ return count;
+};

python/1930-unique-length-3-palindromic-subsequences.py

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+class Solution:
+ def countPalindromicSubsequence(self, s: str) -> int:
+ count = 0
+ chars = set(s)
+ for char in chars:
+ first,last = s.find(char),s.rfind(char)
+ count += len(set(s[first+1:last]))
+ return count

rust/1930-unique-length-3-palindromic-subsequences.rs

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+use std::iter::FromIterator;
+
+impl Solution {
+ pub fn count_palindromic_subsequence(s: String) -> i32 {
+ let mut result = 0;
+ let mut ranges: [(i32, i32); 26] = [(-1, -1); 26];
+
+ for (i, c) in s.chars().enumerate() {
+ let ix = Solution::char_to_index(c) as usize;
+ if ranges[ix].0 == -1 {
+ ranges[ix].0 = i as i32;
+ }
+ if i as i32 > ranges[ix].1 {
+ ranges[ix].1 = i as i32;
+ }
+ }
+
+ for range in ranges {
+ if range.1 > range.0 {
+ let mut set: u32 = 0;
+ for c in s[range.0 as usize + 1..range.1 as usize].chars() {
+ set |= 1 << Solution::char_to_index(c);
+ }
+ result += set.count_ones() as i32;
+ }
+ }
+
+ result
+ }
+
+ pub fn char_to_index(c: char) -> u32 {
+ c as u32 - 'a' as u32
+ }
+}

typescript/1930-unique-length-3-palindromic-subsequences.ts

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+function countPalindromicSubsequence(s: string): number {
+ const alphabets = 'abcdefghijklmnopqrstuvwxyz';
+
+ const N = alphabets.length;
+ let count = 0;
+
+ for (let i = 0; i < N; i += 1) {
+ const ch = alphabets[i];
+ const left = s.indexOf(ch);
+ const right = s.lastIndexOf(ch);
+ if (left < right) {
+ for (const alpha of alphabets) {
+ const mid = s.indexOf(alpha, left + 1);
+ if (mid !== -1 && mid < right) count += 1;
+ }
+ }
+ }
+
+ return count;
+}