LeetCode : Majority Element

思路1

void myQuickSort(vector<int>& nums, int begin, int end)
{
if(begin < end)
{
int l = begin, r = end;
int flag = nums[l];

while(l < r)
{
while(l < r && nums[r] >= flag)
r--;
nums[l] = nums[r];

while(l < r && nums[l] < flag)
l++;
nums[r] = nums[l];
}

nums[l] = flag;
myQuickSort(nums, begin, l - 1);
myQuickSort(nums, l + 1, end);
}
}

int majorityElement(vector<int>& nums)
{
int end = nums.size() - 1;
myQuickSort(nums, 0, end);
return nums[nums.size() / 2];
}

思路2

int Solution::majorityElement(vector<int>& nums)
{
map<int, int> rec;
for(int i = 0; i < nums.size(); i++)
{
if(rec.find(nums[i]) != rec.end())
rec[nums[i]] ++;
else
rec[nums[i]] = 1;
if(rec[nums[i]] > nums.size() / 2)
return nums[i];
}
return -1;
}