Codeforces Round 589 (Div. 2)
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You have $n \times n$ square grid and an integer $k$. Put an integer in each cell while satisfying the conditions below.
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- All numbers in the grid should be between
$1$and$k$inclusive. - Minimum number of the
$i$-th row is$1$($1 \le i \le n$). - Minimum number of the
$j$-th column is$1$($1 \le j \le n$).
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Find the number of ways to put integers in the grid. Since the answer can be very large, find the answer modulo $(10^{9} + 7)$.
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These are the examples of valid and invalid grid when $n=k=2$.
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Input
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The only line contains two integers $n$ and $k$ ($1 \le n \le 250$, $1 \le k \le 10^{9}$).
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Output
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Print the answer modulo $(10^{9} + 7)$.
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Note
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In the first example, following $7$ cases are possible.
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In the second example, make sure you print the answer modulo $(10^{9} + 7)$.
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样例
Input #1
2 2
Output #1
7
InputCopy
OutputCopy
Input #2
123 456789
Output #2
689974806
InputCopy
OutputCopy
题目信息
标签
组合数学
动态规划
数学
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