标签:Subset medium return cur nums int Sum false total
https://leetcode.com/problems/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.
01背包:
class Solution {
public:
bool canPartition(vector<int>& nums) {
int total = accumulate(nums.begin(), nums.end(), 0);
if(total&1) return false;
int target = (total >> 1);
vector<bool> bag(target+1, false);
bag[0] = true;
int last = 0;
for(int cur : nums){
for(int i = min(target, last+cur); i >= cur; --i){
if(bag[i-cur]){
bag[i] = true;
last = max(last, i);
}
}
if(bag[target]) return true;
}
return bag[target];
}
};
DFS剪枝:
越早剪枝越好
class Solution {
public:
int total;
int found = false;
bool canPartition(vector<int>& nums) {
total = accumulate(nums.begin(), nums.end(), 0);
if(total%2) return false;
total >>= 1;
sort(nums.begin(), nums.end(), std::greater<int>());
return dfs(nums, 1, nums[0]);
}
bool dfs(vector<int>& nums, int cur, int num){
if(num == total){
return true;
}
if(cur >= nums.size() || num > total) return false;
return dfs(nums, cur+1, num+nums[cur]) || dfs(nums, cur+1, num);
}
};
标签:Subset,medium,return,cur,nums,int,Sum,false,total 来源: https://blog.csdn.net/Frontier_Setter/article/details/89707022
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