leetcode-4sum原始方法

class Solution {
public:
vector<vector<int>> fourSum(vector<int>& nums, int target) {
int len = nums.size();
sort(nums.begin(),nums.end());

vector<vector<int>> ret;

if(len<4)return ret;

for(int i=0;i<len-3;i++)
{
if(i>0 && nums[i] == nums[i-1])
{
continue;
}
/*if(nums[i] + nums[i+1] + nums[i+2] + nums[i+3] > target)
break;
if(nums[len-1] + nums[len-2] + nums[len-3] + nums[i] < target)
continue;
*/
for(int j=i+1;j<len-2;j++)
{
if(j>i+1 && nums[j] == nums[j-1])
{
continue;
}
/*if(nums[i] + nums[j] + nums[j+1] + nums[j+2] > target)
break;
if(nums[len-1] + nums[len-2] + nums[j] + nums[i] < target)
continue;
*/
int m = j+1;
int n = len - 1;

while(m<n)
{
int sum = nums[i] + nums[j] + nums[m] + nums[n];
if(sum == target )
{

vector<int> tempret;
tempret.push_back(nums[i]);
tempret.push_back(nums[j]);
tempret.push_back(nums[m]);
tempret.push_back(nums[n]);
ret.push_back(tempret);
n--;
while(nums[n] == nums[n+1])
n--;
while(nums[m] == nums[m-1])
m++;
}
else if(sum > target)
{
n--;
while(nums[n] == nums[n+1])
n--;
}
else
{

m++;
while(nums[m] == nums[m-1])
m++;
}

}
}
}
return ret;
}
};