416. Partition Equal Subset Sum

class Solution {
    public boolean canPartition(int[] nums) {
        if (nums == null || nums.length == 0) {
            return true;
        }
        int sum = 0;
        for (int num : nums) {
            sum += num;
        }
        if (sum % 2 != 0) {
            return false;
        }
        sum = sum / 2;
        boolean[] dp = new boolean[sum + 1];
        dp[0] = true;
        for (int i = 0; i < nums.length; i++) {
            for (int j = sum; j >= nums[i]; j--) {
                dp[j] == dp[j] || dp[j - nums[i]]; // 不选/选nums[i]
            }
        }
        return dp[dp.length - 1];
    }
}