findTargetSumWays = (nums, target) => {
    const total = nums.reduce((sum, num) => (sum + num), 0);/* Time O(N) */

    return calculate(nums, target, total);                  /* Time O(N * M) | Space O((N * M) + HEIGHT) */
}
DP - Top Down
Matrix - Memoization
Time O(N * M) | Space O(N * M)
https://leetcode.com/problems/target-sum/
@param {number[]} nums
@param {number} target
@return {number}