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class Solution {
public:
    int maxProfit(vector<int>& prices) {
        //Here how to fix the compilation error which says n is variable size and cant be used for 
        //initialisation  and why does this happen that too in only some Problems;.
         int n=prices.size();
        if(n<=1)
            return 0;
        
        int left[n]={0};
        int mini = prices[0];
        
        for(int i=1;i<n;i++){
           if(prices[i]>mini){
               left[i] = max(left[i-1], prices[i]-mini);
           } 
            else{
                mini=prices[i];
                left[i]=left[i-1];
            }
        }
        int right[n]={0};
        int maxi=prices[n-1];
        
        for(int i=n-2;i>=0;i--){
            if(prices[i]>maxi){
                maxi=prices[i];
                right[i]=right[i+1];
            }
            else{
                right[i] = max(right[i-1], maxi-price[i]);
            }
        }
        int res=0;
        
        for(int i=0;i<n;i++){
            res=max(res, left[i]+right[i]);
        }
        
        return res;
    }
};
Serge Ballesta
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Soumya Ranjan
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    Use std::vector for variable sized arrays. – 273K Mar 24 '21 at 15:36
  • C++ doesn't really have [variable-length arrays](https://en.wikipedia.org/wiki/Variable-length_array), like you try to create for `left` and `right`. – Some programmer dude Mar 24 '21 at 15:37
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    Does this answer your question? [variable-sized object may not be initialized](https://stackoverflow.com/questions/9688219/variable-sized-object-may-not-be-initialized) – 273K Mar 24 '21 at 15:38

1 Answers1

1

From Declerators (8): noptr-declarator [ constexpr(optional) ] attr(optional) (8) the array size is a const expression.

From Array declaration about the size

an integral constant expression (until C++14) a converted constant expression of type std::size_t (since C++14), which evaluates to a value greater than zero

You can't use a runtime variable for this but prices.size() is a runtime variable.

Either use a compile time constant size, a std::vector or dynamic memory allocation.