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 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 Detail

Solution

public Solution()

Method Detail

numRollsToTarget

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