1
impl Solution {
2
  pub fn find_target_sum_ways(nums: Vec<i32>, target: i32) -> i32 {
3
    let mut count = 0;
4
    Self::dfs(&nums, target, 0, 0, &mut count);
5
    count
6
  }
7
  fn dfs(nums: &Vec<i32>, target: i32, current_sum: i32, current_length: usize, res: &mut i32) {
8
    if current_length == nums.len() {
9
      if current_sum == target {
10
        *res += 1;
11
      }
12
      return;
13
    }
14
    let curr_num = nums[current_length];
15
    Self::dfs(
16
      nums,
17
      target,
18
      current_sum + curr_num,
19
      current_length + 1,
20
      res,
21
    );
22
    Self::dfs(
23
      nums,
24
      target,
25
      current_sum - curr_num,
26
      current_length + 1,
27
      res,
28
    );
29
  }
30
}