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| 1 | +// 698. Partition to K Equal Sum Subsets, Medium |
| 2 | +// https://leetcode.com/problems/partition-to-k-equal-sum-subsets/ |
| 3 | +impl Solution { |
| 4 | + pub fn can_partition_k_subsets(mut nums: Vec<i32>, k: i32) -> bool { |
| 5 | + let sum = nums.iter().sum::<i32>(); |
| 6 | + if sum % k != 0 { |
| 7 | + return false; |
| 8 | + } |
| 9 | + let target = sum / k; |
| 10 | + |
| 11 | + nums.sort(); |
| 12 | + if nums[nums.len() - 1] > target { |
| 13 | + return false; |
| 14 | + } |
| 15 | + |
| 16 | + fn backtrack(nums: &Vec<i32>, target: i32, pos: usize, next: i32, used: &mut Vec<bool>) -> bool { |
| 17 | + if used.iter().all(|x| *x) { |
| 18 | + return true; |
| 19 | + } |
| 20 | + |
| 21 | + for i in pos..nums.len() { |
| 22 | + if used[i] || next + nums[i] > target { |
| 23 | + continue; |
| 24 | + } |
| 25 | + |
| 26 | + let next = (next + nums[i]) % target; |
| 27 | + used[i] = true; |
| 28 | + if backtrack(nums, target, if next == 0 { 0 } else { i + 1 }, next, used) { |
| 29 | + return true; |
| 30 | + } |
| 31 | + used[i] = false; |
| 32 | + } |
| 33 | + |
| 34 | + false |
| 35 | + } |
| 36 | + |
| 37 | + backtrack(&nums, target, 0, 0, &mut vec![false; nums.len()]) |
| 38 | + } |
| 39 | +} |
| 40 | + |
| 41 | +struct Solution {} |
| 42 | + |
| 43 | +#[cfg(test)] |
| 44 | +mod tests { |
| 45 | + use super::*; |
| 46 | + |
| 47 | + #[test] |
| 48 | + fn test_can_partition_k_subsets() { |
| 49 | + assert_eq!(Solution::can_partition_k_subsets(vec![4, 3, 2, 3, 5, 2, 1], 4), true); |
| 50 | + } |
| 51 | + |
| 52 | + #[test] |
| 53 | + fn test_can_partition_k_subsets2() { |
| 54 | + assert_eq!(Solution::can_partition_k_subsets(vec![1, 2, 3, 4], 3), false); |
| 55 | + } |
| 56 | + |
| 57 | + #[test] |
| 58 | + fn test_can_partition_k_subsets3() { |
| 59 | + assert_eq!(Solution::can_partition_k_subsets(vec![4, 3, 2, 3, 5, 2, 0], 4), false); |
| 60 | + } |
| 61 | +} |
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