1621. 大小为 K 的不重叠线段的数目

src/main.rs

@@ -1,66 +1,43 @@
-use crate::arr::make_matrix;
+use std::cell::RefCell;
 
 mod arr;
 mod list;
 
 struct Solution {}
 impl Solution {
-    pub fn max_palindromes(s: String, k: i32) -> i32 {
-        let k = k as usize;
-        let mut mat = vec![vec![false; s.len()]; s.len() + 1];
-        let s = s.as_bytes();
-        let (mut af1, mut af2) = (false, true);
-        for i in 0..s.len() {
-            mat[0][i] = true;
-            mat[1][i] = i + 1 < s.len() && s[i] == s[i + 1];
-            af2 &= mat[1][i];
+    pub fn number_of_sets(n: i32, k: i32) -> i32 {
+        let mut mem = vec![vec![vec![-1; n as usize]; n as usize]; 2];
+        let rc = RefCell::new(&mut mem);
+        Self::dfs(&rc, n as usize - 1, k as usize, false) as i32
+    }
+    pub fn dfs(rc: &RefCell<&mut Vec<Vec<Vec<i32>>>>, n: usize, k: usize, is_empty: bool) -> i64 {
+        if k == 0 || n == k {
+            return 1;
         }
-        for i in 2..s.len() {
-            if i % 2 == 0 {
-                if af1 {
-                    continue;
-                }
-            } else if af2 {
-                continue;
-            }
-            let mut local = false;
-            for j in 0..s.len() - i {
-                mat[i][j] = mat[i - 2][j + 1] && s[j] == s[j + i];
-                local |= mat[i][j];
-            }
-            if i%2 == 0 {
-                af1 = !local;
-            }else {
-                af2 = !local;
-            }
+        if n == 0 || n < k {
+            return 0;
         }
-        // for i in 0..s.len() {
-        //     println!("{:?} ", mat[i]);
-        // }
-        let mut events = Vec::new();
-        for i in k - 1 .. s.len() {
-            for j in 0..s.len() - i {
-                if mat[i][j] {
-                    events.push((j, j + i + 1));
-                }
-            }
+        let matrix_idx = if is_empty { 1 } else { 0 };
+        if rc.borrow()[matrix_idx][n][k] != -1 {
+            return rc.borrow()[matrix_idx][n][k] as i64;
         }
-        events.sort_unstable_by(|a,b| a.1.cmp(&b.1));
-        // println!("{:?}", events);
-        let (mut certain,mut ans) = (0,0);
-        for (a,b) in events {
-            if a >= certain {
-                certain = b;
-                ans += 1;
-            }
+        let r#mod = 1e9 as i64 + 7;
+        let mut ans = 0;
+        if !is_empty {
+            ans += Self::dfs(rc, n - 1, k, false) + Self::dfs(rc, n - 1, k, true)
+                - Self::dfs(rc, n - 2, k, true)
+                - Self::dfs(rc, n - 2, k - 1, false);
+            ans = (ans + r#mod) % r#mod;
         }
+
+        ans += Self::dfs(rc, n - 1, k, true) + Self::dfs(rc, n - 1, k - 1, false);
+        ans = ans % r#mod;
+        rc.borrow_mut()[matrix_idx][n][k] = ans as i32;
         ans
     }
 }
 
 fn main() {
-    println!(
-        "{:?}",
-        Solution::max_palindromes("abaccdbbd".to_string(), 3)
-    );
+    println!("{:?}", Solution::number_of_sets(1000, 500));
+    //70047606
 }