feat(backtracking): add 78_subsets.rs

Author: whisperpine

README.md

@@ -19,7 +19,7 @@ flowchart LR
   linked_list("Linked List")
   trees("Trees")
   tries("Tries")
-  backtracing("Backtracing")
+  backtracking("Backtracking")
   %% heap("Heap")
   heap("Heap / Priority Queue")
   graphs("Graphs")
@@ -42,11 +42,11 @@ flowchart LR
   linked_list --> trees
 
   trees --> tries
-  trees --> backtracing
+  trees --> backtracking
   trees --> heap
 
-  backtracing --> dp
-  backtracing --> graphs
+  backtracking --> dp
+  backtracking --> graphs
 
   dp --> bit
   dp --> math
@@ -139,3 +139,9 @@ so that you can use `just tf TEST` command to test.
 | 226. Invert Binary Tree | Easy | [226_invert_binary_tree.rs](./tests/226_invert_binary_tree.rs) |
 | 104. Maximum Depth of Binary Tree | Easy | [104_maximum_depth_of_binary_tree.rs](./tests/104_maximum_depth_of_binary_tree.rs) |
 | 102. Binary Tree Level Order Traversal | Medium | [102_binary_tree_level_order_traversal.rs](./tests/102_binary_tree_level_order_traversal.rs) |
+
+### Backtracking
+
+| Problem | Difficulty | Solution |
+| - | - | - |
+| 78. Subsets | Medium | [78_subsets.rs](./tests/78_subsets.rs) |

tests/78_subsets.rs

@@ -0,0 +1,35 @@
+// 78. Subsets
+// https://leetcode.com/problems/subsets/description/
+// Topics: Backtracking.
+// Difficulty: Medium.
+
+#[test]
+fn test_78_subsets() {}
+
+#[derive(Debug)]
+pub struct Solution;
+
+// ---------------------------------
+// copy to leetcode starts from here
+// ---------------------------------
+
+impl Solution {
+    pub fn subsets(nums: Vec<i32>) -> Vec<Vec<i32>> {
+        let result: Vec<Vec<i32>> = vec![vec![]];
+        recursion(result, nums).0
+    }
+}
+
+fn recursion(mut v: Vec<Vec<i32>>, mut nums_left: Vec<i32>) -> (Vec<Vec<i32>>, Vec<i32>) {
+    let Some(num) = nums_left.pop() else {
+        return (v, nums_left);
+    };
+    let mut new_v = vec![];
+    for item in v.iter() {
+        let mut item = item.clone();
+        item.push(num);
+        new_v.push(item);
+    }
+    v.append(&mut new_v);
+    recursion(v, nums_left)
+}