The teacher wrote a four-digit number on a piece of paper and had 4 rounds of Q&A with Xiaowei. Xiaowei: "Is it 8765?" Teacher: "You guessed two digits correctly, but their positions are wrong." Xiaowei: "Is it 1023?" Teacher: "You guessed two digits correctly, but their positions are wrong." Xiaowei: "Is it 8642?" Teacher: "You guessed two digits correctly, and their positions are correct." Xiaowei: "Is it 5430?" Teacher: "None of the digits are correct." The four-digit number is $\qquad$ -
【Analysis and Solution】Logical Reasoning.
First, according to the 4th Q&A, this four-digit number does not contain the digits $5$, $4$, $3$, $0$;
Then, according to the 2nd Q&A, this four-digit number contains the digits 1, 2;
Next, according to the 3rd Q&A, this four-digit number contains one of the digits 8 or 6;
Combining the 1st Q&A, this four-digit number does not contain the digit 8, otherwise, in the 1st Q&A, Xiao Wei would have at least one digit correct and in the correct position. Therefore, this four-digit number does not contain the digit 8, and the hundred's place is 6, and the unit's place is 2;

Returning to the 2nd Q&A, the digit 1 is not in the thousand's place, so it can only be in the ten's place;
Finally, according to the 1st Q&A, this four-digit number contains the digit 7, and 7 can only be in the thousand's place;
In summary, this four-digit number is 7612.