Package g1101_1200.s1155_number_of_dice_rolls_with_target_sum

Class Solution

java.lang.Object
g1101_1200.s1155_number_of_dice_rolls_with_target_sum.Solution
public class Solution extends java.lang.Object
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 kn 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 109 + 7.

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 109 + 7.

Constraints:

  • 1 <= n, k <= 30
  • 1 <= target <= 1000

  • Constructor Summary

    Constructors
    Constructor
    Description
    Solution()
     

  • Method Summary

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

    Methods inherited from class java.lang.Object

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

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • numRollsToTarget

      public int numRollsToTarget(int n, int k, int target)