47：礼物的最大价值

注意指针数组的建立和删除

int getMaxvalue(const int*matrix, int rows, int cols)
{
    if (matrix == NULL || rows <= 0 || cols <= 0)return 0;
    int **dp = new int*[rows];
    for (int i = 0; i < rows; i++)dp[i] = new int[cols];
    for (int i = 0; i < rows; i++)
    {
        for (int j = 0; j < cols; j++)
        {
            int left = 0, up = 0;
            if (j)left = dp[i][j - 1];
            if (i)up = dp[i - 1][j];
            dp[i][j] = max(left, up) + matrix[i*cols + j];
        }
    }
    int ans=dp[rows - 1][cols - 1];
    for (int i = 0; i < rows; i++)delete[]dp[i];
    delete[]dp;
    return ans;
}

int getMaxvalue(const int*matrix, int rows, int cols)
{
    if (matrix == NULL || rows <= 0 || cols <= 0)return 0;
    int *dp = new int[cols];
    for (int i = 0; i < rows; i++)
    {
        for (int j = 0; j < cols; j++)
        {
            int left = 0, up = 0;
            if (i)up = dp[j];//判断上和左是否存在
            if (j)left = dp[j - 1];
            dp[j] = max(left, up) + matrix[i*cols + j];
        }
    }
    int ans = dp[cols - 1];
    delete[]dp;
    return ans;
}