ucup

Cargo.toml

@@ -1,6 +1,7 @@
 [workspace]
 members = [
-    "main",
+    # "main",
+    # DO not format this file.
     "algo_lib",
 ]
 

algo_lib/src/collections/bit_set.rs

@@ -1,4 +1,4 @@
-use std::ops::{BitAndAssign, BitOrAssign, Not};
+use std::ops::{BitAndAssign, BitOrAssign, BitXorAssign, Not};
 
 #[derive(Hash, Clone, Eq, PartialOrd, PartialEq, Debug)]
 pub struct BitSet {
@@ -39,6 +39,24 @@ impl BitSet {
         res
     }
 
+    // bit [i] becomes [i - shift]. Bits before [0] are dropped.
+    pub fn shift_lower(&self, shift: usize) -> Self {
+        let mut res = Self::new(self.bit_len());
+        let whole = shift / 64;
+        let offset = shift % 64;
+        for i in 0..self.values.len() {
+            if i < whole {
+                continue;
+            }
+            // TODO: test
+            res.values[i - whole] |= self.values[i] >> offset;
+            if offset != 0 && i - whole != 0 {
+                res.values[i - whole - 1] |= self.values[i] << (64 - offset);
+            }
+        }
+        res
+    }
+
     #[allow(unused)]
     pub fn set(&mut self, pos: usize, val: bool) {
         if val {
@@ -163,3 +181,16 @@ impl BitAndAssign<&BitSet> for BitSet {
         }
     }
 }
+
+impl BitXorAssign<&BitSet> for BitSet {
+    fn bitxor_assign(&mut self, rhs: &BitSet) {
+        self.ensure_length(rhs.bit_len());
+        let len = rhs.values.len();
+        for (x, y) in self.values[0..len]
+            .iter_mut()
+            .zip(rhs.values[0..len].iter())
+        {
+            *x ^= *y;
+        }
+    }
+}