I got the answer. It is easy to achieve this goal.

Create two record rules as follows (in your views XML file, where "group_sales_base" is the user group that the rules would be applied to):

<record id="crm_lead_sales_base_rule_personal" model="ir.rule">

    <field name="name">Personal Leads</field>

    <field ref="model_crm_lead" name="model_id"/>

    <field name="domain_force">[('user_id','=',user.id)]</field>

    <field name="groups" eval="[(4, ref('group_sales_base'))]"/>

    <field name="perm_read" eval="True"/>

    <field name="perm_write" eval="True"/>

    <field name="perm_unlink" eval="True"/>

    <field name="perm_create" eval="True"/>

</record>

<record id="crm_lead_sales_base_rule_others" model="ir.rule">

    <field name="name">Others' Leads</field>

    <field ref="model_crm_lead" name="model_id"/>

    <field name="domain_force">['|',('user_id','!=',user.id),('user_id','=',False)]</field>

    <field name="groups" eval="[(4, ref('group_sales_base'))]"/>

    <field name="perm_read" eval="True"/>

    <field name="perm_write" eval="False"/>

    <field name="perm_unlink" eval="False"/>

    <field name="perm_create" eval="False"/>

</record>