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sum4-2.cpp
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sum4-2.cpp
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#include <unordered_map>
#include <iostream>
#include <algorithm>
using namespace std;
#include <unordered_map>
#include <unordered_set>
#include <iostream>
#include <algorithm>
#include <functional>
using namespace std;
struct v4hash
{
size_t operator()(const vector<int>& v) const
{
auto h = hash<int>();
std::size_t seed = v.size();
for(auto& i : v) {
seed ^= h(i) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
}
return seed;
}
};
class Solution {
public:
vector<vector<int>> fourSum(vector<int> nums, int target) {
unordered_set<vector<int>, v4hash> rets;
unordered_map<long, int> hmap;
for(int i = 0; i < nums.size(); ++i){
for(int j = i+1; j < nums.size(); ++j){
hmap.clear();
for(int k = j+1; k < nums.size(); ++k){
if(hmap.find((long)nums[k]) != hmap.end()){
vector<int> temp{nums[i], nums[j], nums[k], nums[hmap[(long)nums[k]]]};
sort(temp.begin(), temp.end()); //确保不同顺序的四元组不会重复
rets.insert(temp);
} else {
hmap[(long)target - (long)nums[k] - (long)nums[i] - (long)nums[j]] = k;
}
}
}
}
vector<vector<int>> ret(rets.begin(), rets.end());
return ret;
}
};