LeetCode Link: 377. Combination Sum IV
Language: C#
Problem Statement
Given an array of distinct integers nums and a target integer target, return the number of possible combinations that add up to target.
The test cases are generated so that the answer can fit in a 32-bit integer.
Example 1:
Input: nums = [1,2,3], target = 4
Output: 7
Explanation:
The possible combination ways are:
(1, 1, 1, 1)
(1, 1, 2)
(1, 2, 1)
(1, 3)
(2, 1, 1)
(2, 2)
(3, 1)
Note that different sequences are counted as different combinations.
Example 2:
Input: nums = [9], target = 3
Output: 0
Constraints:
- 1 <= nums.length <= 200
- 1 <= nums[i] <= 1000
- All the elements of nums are unique.
- 1 <= target <= 1000
Solution
public class Solution
{
public int CombinationSum4(int[] nums, int target)
{
var n = nums.Length;
var dp = new int[target + 1];
dp[0] = 1;
for (int i=0; i<dp.Length; i++)
{
for (int j = 0; j<nums.Length; j++)
{
if (i - nums[j] < 0)
{
continue;
}
dp[i] += dp[i-nums[j]];
}
}
return dp[target];
}
}