diff --git a/src/main.rs b/src/main.rs
index a9d800f..9cd62b5 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,34 +1,38 @@
-mod arr;
+use std::collections::HashSet;
+
 struct Solution;
 impl Solution {
-    pub fn intersection_size_two(intervals: Vec<Vec<i32>>) -> i32 {
-        let mut tasks = intervals;
-        tasks.sort_by_key(|task| task[1]);
-        let mut stack:Vec<Vec<i32>> = Vec::new();
-        stack.push(vec![-2,-2,0]);
-        for task in tasks.iter() {
-            let start = task[0];
-            let end = task[1];
-            let mut d = 2;
-            let pos = stack.partition_point(|x| x[0] < start) - 1;
-            d -= stack[stack.len() - 1][2] - stack[pos][2];
-            if start <= stack[pos][1] {
-                d -= stack[pos][1] - start + 1;
+    pub fn count_palindromic_subsequence(s: String) -> i32 {
+        let mut ans = 0;
+        let s = s.bytes().collect::<Vec<u8>>();
+        let mut set : HashSet<u8> = HashSet::new();
+        for c in b'a'..=b'z' {
+            set.clear();
+            let (mut start,mut end) = (-1,0);
+            for i in 0..s.len() {
+                if s[i] == c {
+                    start = i as i32;
+                    break;
+                }
             }
-            if d <= 0{
+            if start == -1 {
                 continue;
             }
-            while end - stack[stack.len() - 1][1] <= d {
-                let end = stack.pop().unwrap();
-                d += end[1] - end[0] + 1;
+            for i in (0..s.len()).rev() {
+                if s[i] == c {
+                    end = i;
+                    break;
+                }
             }
-            stack.push(vec![end - d + 1, end,stack[stack.len() - 1][2] + d]);
+            for i in (start+1)as usize..end {
+                set.insert(s[i]);
+            }
+            ans += set.len() as i32;
         }
-        stack[stack.len() - 1][2]
+        ans
     }
 }
-
 fn main() {
-    let result = Solution::intersection_size_two(arr::make_matrix("[[1,3],[3,7],[8,9]]"));
+    let result = Solution::count_palindromic_subsequence(String::from("bbcbaba"));
     println!("{:?}", result);
 }