38 lines
828 B
Go
38 lines
828 B
Go
// Package q216 implements a solution for https://leetcode.com/problems/combination-sum-iii/
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package q216
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// k numbers sum up to n
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func calc(k int, buf []int, offset int, remSum int, ret [][]int) [][]int {
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if offset == k-1 && remSum > 0 && remSum < 10 {
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buf[offset] = remSum
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cp := make([]int, len(buf))
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copy(cp, buf)
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return append(ret, cp)
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}
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remK := k - offset
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minI := 1
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if offset > 0 {
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minI = buf[offset-1] + 1
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}
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maxI := 9 - remK + 1
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for i := minI; i <= maxI; i++ {
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minSum := (i + i + remK - 1) * remK / 2
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maxSum := (19 - remK) * remK / 2
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if remSum < minSum || remSum > maxSum {
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continue
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}
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buf[offset] = i
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ret = calc(k, buf, offset+1, remSum-i, ret)
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}
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return ret
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}
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func combinationSum3(k int, n int) [][]int {
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return calc(k, make([]int, k), 0, n, [][]int{})
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}
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var _ = combinationSum3
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