From f3ad87f0f957f395d4c3220845773b7d634582cd Mon Sep 17 00:00:00 2001
From: xw_y_am <xw_y_am@163.com>
Date: Fri, 22 Feb 2019 02:59:26 +0800
Subject: [PATCH] add fibnacci serial

---
 fibnacci_serial/v.cpp | 90 +++++++++++++++++++++++++++++++++++++++++++
 fibnacci_serial/v.py  | 17 ++++++++
 2 files changed, 107 insertions(+)
 create mode 100644 fibnacci_serial/v.cpp
 create mode 100644 fibnacci_serial/v.py

diff --git a/fibnacci_serial/v.cpp b/fibnacci_serial/v.cpp
new file mode 100644
index 0000000..4086196
--- /dev/null
+++ b/fibnacci_serial/v.cpp
@@ -0,0 +1,90 @@
+#include <vector>
+#include <iostream>
+
+using namespace std;
+
+#define UNIT        100000000
+#define UNIT_LEN    8
+const char *zero = "00000000";
+
+typedef vector<int> BN;
+
+string BN_str(BN *b)
+{
+    string sn = to_string(b->at(b->size() - 1));
+    for (int i = b->size() - 2; i >= 0; i--) {
+        string su = to_string(b->at(i));
+        if (su.length() < UNIT_LEN) {
+            sn += (zero + su.length());
+        }
+        sn += su;
+    }
+    return sn;
+}
+
+int BN_len(BN *b)
+{
+    if (!b->size()) return 0;
+    int l = 0;
+    for (int h = b->back(); h; h /= 10) l += 1;
+    return (b->size() - 1) * UNIT_LEN + l;
+}
+
+BN BN_init(int x)
+{
+    BN v;
+    v.push_back(x);
+    return v;
+}
+
+void BN_merge(BN *a, BN *b)
+{
+    int carry_up = 0;
+    int ib = 0;
+    for (int ia = 0; ia < a->size(); ia++, ib++) {
+        carry_up += a->at(ia) + b->at(ib);
+        (*a)[ia] = carry_up % UNIT;
+        carry_up /= UNIT;
+    }
+    for (; ib < b->size(); ib++) {
+        carry_up += b->at(ib);
+        a->push_back(carry_up % UNIT);
+        carry_up /= UNIT;
+    }
+    for (; carry_up; carry_up /= UNIT) {
+        a->push_back(carry_up % UNIT);
+    }
+}
+
+int BN_digit(BN *a, int n)
+{
+    string sn = BN_str(a);
+    if (n > sn.length()) return -1;
+    return sn[n - 1] - '0';
+}
+
+int digit_of_fib_digit(int n)
+{
+    BN a = BN_init(1);
+    BN b = BN_init(1);
+    BN *p = &a;
+    BN *q = &b;
+    for (;;) {
+        cout << BN_str(p) << endl;
+        int l = BN_len(p);
+        if (l >= n) {
+            return BN_digit(p, n);
+        }
+        n -= l;
+        BN_merge(p, q);
+        BN *t = p;
+        p = q;
+        q = t;
+    }
+}
+
+int main()
+{
+    cout << digit_of_fib_digit(800) << endl;
+    return 0;
+}
diff --git a/fibnacci_serial/v.py b/fibnacci_serial/v.py
new file mode 100644
index 0000000..4de1722
--- /dev/null
+++ b/fibnacci_serial/v.py
@@ -0,0 +1,17 @@
+
+def gen_fib():
+    a, b = 0, 1
+    while True:
+        yield b
+        a, b = b, a + b
+
+def digit_in_fib(n):
+    for x in gen_fib():
+        print(x)
+        s = str(x)
+        l = len(s)
+        if l >= n:
+            return s[n - 1]
+        n -= l
+
+print(digit_in_fib(800))