LeetCode 416 Partition Equal Subset Sum (dp 01背包)

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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:

1. Each of the array element will not exceed 100.
2. 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.

题目链接：https://leetcode.com/problems/partition-equal-subset-sum/

题目分析：sum必须是偶数，对sum/2，进行01背包dp

8ms，时间击败87.5%

class Solution {
    public boolean canPartition(int[] nums) {
        int sum = 0;
        for (int i = 0; i < nums.length; i++) {
            sum += nums[i];
        }
        if ((sum & 1) == 1) {
            return false;
        }
        int target = sum >> 1;
        boolean[] dp = new boolean[target + 1];
        dp[0] = true;
        for (int i = 0; i < nums.length; i++) {
            for (int j = target; j >= nums[i]; j--) {
                if (dp[j - nums[i]]) {
                    if (j == target) {
                        return true;
                    }
                    dp[j] = true;
                }
            }
        }
        return false;
    }
}

本题最快的做法是sort完了DFS剪枝