Package g1101_1200.s1155_number_of_dice_rolls_with_target_sum

Class Solution

  • All Implemented Interfaces:
    
public final class Solution

    1155 - Number of Dice Rolls With Target Sum.

    Medium

    You have n dice and each die has k faces numbered from 1 to k.

    Given three integers n, k, and target, return the number of possible ways (out of the <code>k<sup>n</sup></code> total ways) to roll the dice so the sum of the face-up numbers equals target. Since the answer may be too large, return it modulo <code>10<sup>9</sup> + 7</code>.

    Example 1:

    Input: n = 1, k = 6, target = 3

    Output: 1

    Explanation: You throw one die with 6 faces.

    There is only one way to get a sum of 3.

    Example 2:

    Input: n = 2, k = 6, target = 7

    Output: 6

    Explanation: You throw two dice, each with 6 faces.

    There are 6 ways to get a sum of 7: 1+6, 2+5, 3+4, 4+3, 5+2, 6+1.

    Example 3:

    Input: n = 30, k = 30, target = 500

    Output: 222616187

    Explanation: The answer must be returned modulo 10<sup>9</sup> + 7.

    Constraints:

    • 1 &lt;= n, k &lt;= 30

    • 1 &lt;= target &lt;= 1000

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description

    • Field Summary

      Fields 
      Modifier and Type Field Description

    • Constructor Summary

      Constructors 
      Constructor Description
      Solution()

    • Enum Constant Summary

      Enum Constants 
      Enum Constant Description

    • Method Summary

      Modifier and Type Method Description
      final Integer numRollsToTarget(Integer n, Integer k, Integer target)

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait