58 lines
1.4 KiB
Plaintext
58 lines
1.4 KiB
Plaintext
function fannkuch(n) {
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var perm1 = [n]
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for (let i = 0; i < n; i++) perm1[i] = i
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var perm = [n]
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var count = [n]
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var f = 0, flips = 0, nperm = 0, checksum = 0
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var i, k, r
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r = n
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while (r > 0) {
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i = 0
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while (r != 1) { count[r-1] = r; r -= 1 }
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while (i < n) { perm[i] = perm1[i]; i += 1 }
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// Count flips and update max and checksum
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f = 0
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k = perm[0]
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while (k != 0) {
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i = 0
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while (2*i < k) {
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let t = perm[i]; perm[i] = perm[k-i]; perm[k-i] = t
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i += 1
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}
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k = perm[0]
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f += 1
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}
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if (f > flips) flips = f
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if ((nperm & 0x1) == 0) checksum += f; else checksum -= f
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// Use incremental change to generate another permutation
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var more = true
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while (more) {
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if (r == n) {
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log.console( checksum )
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return flips
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}
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let p0 = perm1[0]
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i = 0
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while (i < r) {
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let j = i + 1
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perm1[i] = perm1[j]
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i = j
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}
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perm1[r] = p0
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count[r] -= 1
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if (count[r] > 0) more = false; else r += 1
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}
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nperm += 1
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}
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return flips;
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}
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var n = arg[0] || 10
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log.console(`Pfannkuchen(${n}) = ${fannkuch(n)}`)
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$stop() |