41 lines
1 KiB
Swift
41 lines
1 KiB
Swift
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class Solution {
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private struct Solver {
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let k, n: Int
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var combinations: [[Int]]
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init(k: Int, n: Int) {
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self.k = k
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self.n = n
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self.combinations = []
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}
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mutating func solve() {
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var combination: [Int] = []
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solve(&combination, k: k, n: n, nextDigit: 1)
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}
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private mutating func solve(_ combination: inout [Int], k: Int, n: Int, nextDigit: Int) {
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if k == 0 && n == 0 {
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combinations.append(combination)
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return
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}
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if k <= 0 || n <= 0 || nextDigit > 9 {
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return
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}
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for d in nextDigit...9 {
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combination.append(d)
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solve(&combination, k: k - 1, n: n - d, nextDigit: d + 1)
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_ = combination.popLast()
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}
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}
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}
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func combinationSum3(_ k: Int, _ n: Int) -> [[Int]] {
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var s = Solver(k: k, n: n)
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s.solve()
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return s.combinations
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}
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}
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