reverse bits solution

Author: yhkee0404

reverse-bits/yhkee0404.rs

@@ -0,0 +1,31 @@
+use std::sync::OnceLock;
+
+static _TABLE: OnceLock<Vec<i32>> = OnceLock::new();
+
+impl Solution {
+
+    pub fn reverse_bits(mut n: i32) -> i32 {
+        let mut x: u32 = 0;
+        for i in 0..6 {
+            let shift = if i == 5 {2} else {6} as u32;
+            x = x << shift | Self::init_table()[(n & (1 << shift) - 1) as usize] as u32 >> 6 - shift;
+            n >>= 6;
+        }
+        x as i32
+    }
+    
+    fn init_table() -> &'static Vec<i32> {
+        _TABLE.get_or_init(|| {
+            let mut table: Vec<i32> = vec![0; 1 << 6];
+            for (i, x) in table.iter_mut().enumerate() {
+                let mut j = i as i32;
+                for k in 0..6 {
+                    *x = *x << 1 | j & 1;
+                    j >>= 1;
+                }
+            }
+            table
+        })
+    }
+
+}