LeetCode 416. Partition Equal Subset Sum

Given a non-empty array containing only positive integers, find if the array can be partitioned into two subsets such that the sum of elements in both subsets is equal.

Note:

Each of the array element will not exceed 100.
The array size will not exceed 200.
Example 1:

Input: [1, 5, 11, 5]

Output: true

Explanation: The array can be partitioned as [1, 5, 5] and [11].

Example 2:

Input: [1, 2, 3, 5]

Output: false

Explanation: The array cannot be partitioned into equal sum subsets.

分析

这道题用动态规划，dp[i] 表示是否能从数组中取得数字之和为i , 动态转移方程dp[i]=dp[i]||dp[i-n] .

class Solution {
public:
    bool canPartition(vector<int>& nums) {
         int s=accumulate(nums.begin(),nums.end(),0);
         if(s%2!=0) return false;
         vector<int> dp(s/2+1,0);
         dp[0]=1;
         vector<int> visited(s/2+1,0);
         for(auto o:nums)
             for(int i=s/2;i>=o;i--)
                 dp[i]=dp[i-o]||dp[i];
         return dp[s/2]==1;
    }
};