416. Partition Equal Subset Sum

解题思路：

1. 用双循环去更新dp[j]：dp[j] = dp[j] || dp[j - nums[i]]

代码：

class Solution {
public boolean canPartition(int[] nums) {

    int len = nums.length;
    int sum = 0;
    for(int i = 0; i < len; i++){
        sum += nums[i];
    }
    if(sum % 2 != 0) return false; 
    int target = sum/2;
    boolean[] dp = new boolean[target + 1];
    dp[0] = true;
    for(int i = 1; i <= len; i++){
        for(int j = target; j >= nums[i - 1]; j--){
            dp[j] = dp[j] || dp[j - nums[i - 1]];
        }
    }
    return dp[target];
}

}