Rewrite these sentences using the past perfect tense:

Here are the rewritten sentences:

1. She realized she was lost after she had walked a lot.
2. The train had left before we reached the platform.
3. After he had said something offensive earlier, he apologized.
4. By the time the police arrived, the thief had escaped.
5. The boys had bought a ball before they played football.
6. They were exhausted after they had trained without a break.