LC494. 目标和

class Solution {


    public int findTargetSumWays(int[] nums, int target) {

        int sum  = 0 ;
        for(int i = 0 ; i < nums.length; i ++){
            sum += nums[i];
        }

        if(target < 0 && sum < - target){
            return 0;
        }


        if((target + sum) % 2 != 0) return 0;

        int size = (target + sum) / 2;

        if(size < 0) size = -size;

        int [] dp = new int[size+1];

        dp[0] = 1;

        for(int i = 0 ; i < nums.length; i ++){

            for(int j = size ; j >= nums[i] ; j --){
                dp[j] += dp[j - nums[i]];
            }

        }

        return dp[size];


    }
}