LeetCode 377: Combination Sum IV Solution

Master LeetCode problem 377 (Combination Sum IV), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

377. Combination Sum IV

Medium

Array Dynamic Programming

Problem Explanation

Explanation:

To solve this problem, we can use dynamic programming. We create an array dp where dp[i] represents the number of combinations that add up to i. We initialize dp[0] = 1 since there is one way to get a sum of 0.

For each target sum i from 1 to the given target, we iterate through the input array nums to find all possible combinations that can achieve the sum i. We update dp[i] by adding the number of combinations found.

Finally, the result is stored in dp[target], which represents the total number of combinations that add up to the target.

Time Complexity:

The time complexity of this solution is O(target * nums.length) since we iterate through each target value and each element in the nums array.

Space Complexity:

The space complexity is O(target) for the dp array.

Solution Code

class Solution {
    public int combinationSum4(int[] nums, int target) {
        int[] dp = new int[target + 1];
        dp[0] = 1;
        
        for (int i = 1; i <= target; i++) {
            for (int num : nums) {
                if (i - num >= 0) {
                    dp[i] += dp[i - num];
                }
            }
        }
        
        return dp[target];
    }
}

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