【leetcode刷题】T171-分割等和子集

示例 1:
输入: [1, 5, 11, 5]
输出: true
解释: 数组可以分割成 [1, 5, 5] 和 [11].

示例 2:
输入: [1, 2, 3, 5]
输出: false
解释: 数组不能分割成两个元素和相等的子集.

class Solution(object):
    def canPartition(self, nums):
        """
        :type nums: List[int]
        :rtype: bool
        """
        # 2 * 单个数组和，肯定是偶数
        target = sum(nums)
        if target % 2 == 1:
            return False

        # 选择n个数，和为target
        target = target / 2
        dp = [False] * (target + 1)
        dp[0] = True
        for n in nums:
            ls = []
            for i in range(len(dp)-1, -1, -1):
                # i可以，那么i+n可以
                if dp[i] and i + n <= target:
                    dp[i+n] = True

        return dp[-1]

class Solution {
public:
    bool canPartition(vector<int>& nums) {
        int sum0 = 0;
        for(auto n: nums)
            sum0 += n;
        // 只有和是偶数，才可能分成两个和相等的数组
        if(sum0 % 2 == 1)
            return false;

        // 选择n个数，和为target
        int target =  sum0 / 2;
        vector<int> dp(target+1, false);
        dp[0] = true;
        for(auto n: nums){
            for(int i = target; i >= 0; i--){
                if(dp[i] && i + n <= target)
                    dp[i+n] = true;
            }
        }
        return dp.back();
    }
};