LeetCode 494. Target Sum

Problem Statement

impl Solution {
    fn dfs(nums: &Vec<i32>, index: i32, sum: i32, s: i32, ans: &mut i32) {
        if index == nums.len() as i32 {
            if sum == s {
                *ans += 1;
            }
            return;
        }

        Self::dfs(nums, index + 1, sum + nums[index as usize], s, ans);
        Self::dfs(nums, index + 1, sum - nums[index as usize], s, ans);
    }
    pub fn find_target_sum_ways(nums: Vec<i32>, s: i32) -> i32 {
        let mut ans = 0;
        Self::dfs(&nums, 0, 0, s, &mut ans);
        return ans;
    }
}