Combination sum iv

Array Dynamic Programming

55.0% acceptance

Jan 12, 2026

7755

699

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.

Solution

Rust

Time O(n²)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn combination_sum4(nums: Vec<i32>, target: i32) -> i32 {
    let target = target as usize;
    let mut dp = vec![0; target + 1];
    dp[0] = 1;
    
    for i in 1..=target {
      for &num in &nums {
        if num as usize <= i {
          dp[i] += dp[i - num as usize];
        }
      }
    }
    
    dp[target]
  }
}