588 - Partition Equal Subset Sum

本文探讨了一道难度较高的子集划分问题,并提供了一个简洁的Java解决方案。通过对问题的深入剖析,采用动态规划的方法判断一个整数数组是否可以被划分为两个子集,使得每个子集的元素之和相等。

2017.9.6.

题目真的是越来越难了呢,很多思路我完全没有。别人的思路和代码也是勉勉强强可以看懂,但是自己是完全写不出来那么巧妙的思路的。

这个题目加收藏了,一定还是要好好琢磨的。

public class Solution {
    /**
     * @param nums a non-empty array only positive integers
     * @return return true if can partition or false
     */
	public boolean canPartition(int[] nums) {
        // Write your code here
        int length = nums.length;
        if(length <= 1){
            return false;
        }
        int sum = 0;
        for(int num : nums){
        	sum += num;
        }
        if(sum%2 == 1){
        	return false;
        }
        
        sum /= 2;
        boolean []dp = new boolean[sum + 1];
        //dp【i】用来表示,数组中是否存在 和为 i 的子集合。
        //状态转移,感觉真是巧妙啊。
        dp[0] = true;
        for(int i = 0; i < length; i++){
        	for(int j = sum; j>= nums[i]; j--){
        		dp[j] = dp[j] || dp[j - nums[i]];
        	}
        }
        return dp[sum];  
    }
}


Write a C program that can be run in the Microsoft Visual Studio to partitions a hypergraph G = (V, E) into 2 partitions. The Assignment Write a computer program that takes a netlist represented by a weighted hypergraph and partitions it into two partitions. Each node is associated with an area value and each edge has an edge cost. Your program should minimize the total cost of the cut set, while satisfying the area constraint that the total area of partition 1 should satisfy the balance criteria as described in the class. That is, if the area sum of all the nodes is A, then the area of partition 1 should be greater than or equal to ra-tio_factor *A – amax and less than or equal to ratio_factor *A + amax, where amax is the maximum value among all cell areas. The program should prompt the user for the value of ratio_factor. Assumptions and Requirements of the Implementation Your program should not have any limitation on the maximum number of nodes and the edges of the hypergraph. Each hyperedge could connect any subset of nodes in the hypergraph. Each node area is a non-negative integer, and each edge cost is a non-negative floating- point value. All the ids are 0-based. Namely, the id of the first element is 0, instead of 1. The output of each partition should include the list of node ids, sorted in the ascending order. The partition with the smaller minimum node id is listed first in the output. Use balance criteria as the tiebreaker when there are multiple cell moves giving the max-imum gain, as described in the class. Use the input and output formats given in the Sample Test Cases section. Sample Test Cases Test: Please enter the number of nodes: 4 Please enter each of the 4 nodes with its id and the node area: 0 1 1 4 2 2 3 1 Please enter the number of edges: 3 Please enter each of the 3 edges with the number of connected nodes and their node ids, followed by the edge cost: 3 0 1 2 5 3 0 2 3 3 3 0 1 3 4 Please enter the percentage of ratio factor: 50 The node ids of the partition 0 are 3 The node ids of the partition 1 are 0, 1, 2 The total cut cost is 7
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