Data commit

Task/Partition-function-P/Go/partition-function-p.go

@@ -0,0 +1,59 @@
+package main
+
+import (
+    "fmt"
+    "math/big"
+    "time"
+)
+
+var p []*big.Int
+var pd []int
+
+func partDiffDiff(n int) int {
+    if n&1 == 1 {
+        return (n + 1) / 2
+    }
+    return n + 1
+}
+
+func partDiff(n int) int {
+    if n < 2 {
+        return 1
+    }
+    pd[n] = pd[n-1] + partDiffDiff(n-1)
+    return pd[n]
+}
+
+func partitionsP(n int) {
+    if n < 2 {
+        return
+    }
+    psum := new(big.Int)
+    for i := 1; i <= n; i++ {
+        pdi := partDiff(i)
+        if pdi > n {
+            break
+        }
+        sign := int64(-1)
+        if (i-1)%4 < 2 {
+            sign = 1
+        }
+        t := new(big.Int).Mul(p[n-pdi], big.NewInt(sign))
+        psum.Add(psum, t)
+    }
+    p[n] = psum
+}
+
+func main() {
+    start := time.Now()
+    const N = 6666
+    p = make([]*big.Int, N+1)
+    pd = make([]int, N+1)
+    p[0], pd[0] = big.NewInt(1), 1
+    p[1], pd[1] = big.NewInt(1), 1
+    for n := 2; n <= N; n++ {
+        partitionsP(n)
+    }
+    fmt.Printf("p[%d)] = %d\n", N, p[N])
+    fmt.Printf("Took %s\n", time.Since(start))
+}