leetcode: Add subsets

leetcode/0078.subsets/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "lc-0078-subsets"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+[dependencies]

leetcode/0078.subsets/src/main.rs

@@ -0,0 +1,65 @@
+// Copyright (c) 2023 Xu Shaohua <[email protected]>. All rights reserved.
+// Use of this source is governed by General Public License that can be
+// found in the LICENSE file.
+
+pub fn get_all<T: Copy>(out: &mut Vec<Vec<T>>, data: &[T], chunk_len: usize) {
+    if chunk_len == 0 {
+        out.push(Vec::new());
+        return;
+    }
+    if chunk_len == data.len() {
+        out.push(data.to_vec());
+        return;
+    }
+
+    let len = data.len();
+    let min = 2_usize.pow(chunk_len as u32) - 1;
+    let mut mask = 2_usize.pow(len as u32) - 2_usize.pow((len - chunk_len) as u32);
+
+    fn get_chunk<T: Copy>(mask: usize, data: &[T]) -> Vec<T> {
+        let b = format!("{:01$b}", mask, data.len());
+        b.chars()
+            .enumerate()
+            .filter(|&(_, e)| e == '1')
+            .map(|(i, _)| data[i])
+            .collect()
+    }
+
+    while mask >= min {
+        if mask.count_ones() as usize == chunk_len {
+            let res = get_chunk(mask, data);
+            mask -= 1;
+            out.push(res);
+        } else {
+            mask -= 1;
+        }
+    }
+}
+
+// Combinations
+pub fn subsets(nums: Vec<i32>) -> Vec<Vec<i32>> {
+    let mut out = vec![];
+    for i in 0..=nums.len() {
+        get_all(&mut out, &nums, i);
+    }
+    out
+}
+
+fn main() {
+    let nums = vec![1, 2, 3];
+    let expected_out = vec![
+        vec![],
+        vec![1],
+        vec![2],
+        vec![3],
+        vec![1, 2],
+        vec![1, 3],
+        vec![2, 3],
+        vec![1, 2, 3],
+    ];
+    assert_eq!(subsets(nums), expected_out);
+
+    let nums = vec![0];
+    let expected_out = vec![vec![], vec![0]];
+    assert_eq!(subsets(nums), expected_out);
+}