Function find_target_sum_ways2

pub fn find_target_sum_ways2(nums: Vec<i32>, s: i32) -> i32

analysis and dp sum(P) - sum(N) = target sum(P) + sum(N) + sum(P) - sum(N) = target + sum(P) + sum(N) 2 * sum(P) = target + sum(nums) so, if target + sum(nums) is not even, return 0, else get sum(P) == (target + sum(nums))/2