力扣1793.好子数组的最大分数

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  • 对于每个数 求其左右两侧小于它高度的元素下标(单调栈)

•   class Solution {public:int maximumScore(vector<int>& nums, int k) {int n = nums.size();vector<int> left(n,-1);stack<int> st;for(int i=0;i<n;i++){while(!st.empty()&& nums[i] <= nums[st.top()])st.pop();if(!st.empty())left[i] = st.top();st.emplace(i);}vector<int> right(n,n);//清空stst = stack<int> ();for(int i=n-1;i>=0;i--){while(!st.empty()&& nums[i] <= nums[st.top()])st.pop();if(!st.empty())right[i] = st.top();st.emplace(i);}int res=0;for(int i=0;i<n;i++){int h = nums[i],l = left[i],r = right[i];if(l<k && k<r)res = max(res,h * (r - l - 1));}return res;}};