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:

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

Example 2:

Input: [1, 2, 3, 5]Output: falseExplanation: The array cannot be partitioned into equal sum subsets.

我们定义一个一维的dp数组，其中dp[i]表示数字i是否是原数组的任意个子集合之和，那么我们我们最后只需要返回dp[target]就行了。

我们需要更新我们的dp数组，要更新[nums[i], target]之间的值，那么对于这个区间中的任意一个数字j，如果dp[j - nums[i]]为true的话，那么dp[j]就一定为true

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;        int target = sum / 2;        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--) {                dp[j] = dp[j] || dp[j - nums[i]];            }        }        return dp[target];    }