698. Partition to K Equal Sum Subsets
Given an integer array nums and an integer k, return true if it is possible to divide this array into k non-empty subsets whose sums are all equal.
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| class Solution {
int dp[1<<16];
vector<int> combs;
void buildComb(vector<int>& A, int comb, int sum, unordered_set<int>& vis) {
if(!sum) {combs.push_back(comb);}
else if(vis.count(comb)) return;
else {
vis.insert(comb);
for(int i = 0; i < A.size() and A[i] <= sum; i++) {
if(comb & (1<<i)) continue;
buildComb(A,comb | (1<<i), sum - A[i], vis);
}
}
}
int helper(vector<int>& A, int mask) {
if(dp[mask] != -1) return dp[mask];
dp[mask] = 0;
for(auto& comb : combs) {
if(comb & mask) continue;
if(helper(A,mask | comb)) return 1;
}
return 0;
}
public:
bool canPartitionKSubsets(vector<int>& nums, int k) {
int sum = accumulate(begin(nums),end(nums),0), n;
if(sum % k) return false;
sum /= k;
sort(begin(nums),end(nums));
if(nums.back() > sum) return false;
while(!nums.empty() and nums.back() == sum) nums.pop_back();
n = nums.size();
memset(dp,-1,sizeof(dp));
buildComb(nums, 0, sum, unordered_set<int>() = {});
dp[(1<<n) - 1] = 1;
return helper(nums, 0);
}
};
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