leetcode刷题，总结，记录，备忘 80

leetcode80 Remove Duplicates from Sorted Array II

Follow up for "Remove Duplicates":

What if duplicates are allowed at most twice?

For example,

Given sorted array nums = 

[1,1,1,2,2,3]

,

Your function should return length = 

5

, with the first five elements of nums being 

1

, 

1

, 

2

, 

2

 and 

3

.
It doesn't matter what you leave beyond the new length.

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题目要求是最多保留2个相同，第三个删掉。这里我灵机一动，想了个绝妙的方法。使用2个set容器，在遍历数组的时候，根据奇偶次数，分别往2个不同的set容器里插入数值，保证每个相同的只有2个数会被成功插入，如果有第三个就会插入失败，此时删掉他，最后返回2个set容器的长度和即可。
class Solution {
public:
int removeDuplicates(vector<int>& nums) {
set<int> s1;
set<int> s2;

for (int i = 0; i < nums.size(); ++i)
{
pair<set<int>::iterator, bool> p;
if (i % 2 == 0)
{
p = s1.insert(nums[i]);
if (p.second == false)
{
nums.erase(nums.begin() + i);
i--;
}
}
else
{
p = s2.insert(nums[i]);
if (p.second == false)
{
nums.erase(nums.begin() + i);
i--;
}
}
}

return s1.size() + s2.size();
}
};