# Two different solutions accepted as best 4ms in C++ enclosed with a basic DP solution

• ``````class Solution {
private:
int binarySearch(int* nums, int size, int target)
{
int l=0, r=size-1;
while(l < r)
{
int m = l+(r-l)/2;
if(nums[m] > target) r = m-1;
else if(nums[m] < target) l = m+1;
else break;
}
if(nums[l] < target) return l+1; //ensure the index is pointed to the position whose element is equal to or bigger than the target;
else return l;
}

public:
//AC - 4ms - using stack to collect the LIS;
int lengthOfLIS(vector<int>& nums)
{
int size = nums.size();
int top = -1;
int *arr = (int*)malloc(sizeof(int)*size);
for(int i = 0; i < size; i++)
{
int pos = binarySearch(arr, top+1, nums[i]);
if(pos > top) arr[++top] = nums[i]; //a new element should be appended;;
else arr[pos] = nums[i]; //make the element pos pointing to smaller;
}
}

//AC - 4ms - C++ way;
int lengthOfLIS(vector<int>& nums)
{
vector<int> collector;
for(int i = 0; i < nums.size(); ++i)
{
auto iter = std::lower_bound(collector.begin(), collector.end(), nums[i]);
if(iter == collector.end()) collector.push_back(nums[i]);
else *iter = nums[i];
}
return collector.size();
}

//AC - 120ms - DP solution;
int lengthOfLIS(vector<int>& nums)
{
int size = nums.size();
if(!size) return 0;
int subLens[size];
subLens[0] = 1;
int maxLen = 1;
for(int i = 1; i < size; ++i)
{
subLens[i] = 1;
for(int j = i-1; j >= 0; --j)
{
if(nums[i] > nums[j]) subLens[i] = max(subLens[i], subLens[j]+1);
maxLen = max(maxLen, subLens[i]);
}
}
return maxLen;
}
};``````

Looks like your connection to LeetCode Discuss was lost, please wait while we try to reconnect.