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19 lines
331 B
19 lines
331 B
package popcount
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var pc [256]byte
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func init() {
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for i := range pc {
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pc[i] = pc[i/2] + byte(1&i)
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}
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}
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func PopCount(x uint64) int {
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return int(pc[byte(x>>(0*8))] +
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pc[byte(x>>(1*8))] +
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pc[byte(x>>(2*8))] +
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pc[byte(x>>(3*8))] +
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pc[byte(x>>(4*8))] +
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pc[byte(x>>(5*8))] +
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pc[byte(x>>(6*8))] +
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pc[byte(x>>(7*8))])
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}
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