数组类型int [n] [n]是不可分配的，因为表达式必须具有常量值

Question

我得到一个错误：表达式必须在第4行上具有一个常量值（int cost [n] [n]），并在此基础上进一步出错，即“数组类型int [n] [n]是不可分配的” “。 我该如何解决？

 int optimalSearchTree(int keys[], int freq[],  int n)
    {
        /* Create an auxiliary 2D matrix to store results of subproblems */

        int cost[n][n];
        for (int i = 0; i < n; i++)
            cost[i][i] = freq[i];

        for (int L = 2; L <= n; L++)
        {
            // i is row number in cost[][]
            for (int i = 0; i <= n - L + 1; i++)
            {
                // Get column number j from row number i and chain length L
                int j = i + L - 1;
                cost[i][j] = INT_MAX;

                // Try making all keys in interval keys[i..j] as root
                for (int r = i; r <= j; r++)
                {
                    // c = cost when keys[r] becomes root of this subtree
                    int c = ((r > i) ? cost[i][r - 1] : 0) +
                        ((r < j) ? cost[r + 1][j] : 0) +
                        sum(freq, i, j);
                    if (c < cost[i][j])
                        cost[i][j] = c;
                }
            }
        }
        return cost[0][n - 1];
    }

Answer 1

在c ++中创建动态n * n大小的2d数组的标准方法是这样的

std::vector<std::vector<int> > cost(n,std::vector<int>(n));

请参阅Vector of vectors, reserve