From 3833c952f1dff3957bc423045df6d52c14a6db78 Mon Sep 17 00:00:00 2001
From: Santo Cariotti <dcariotti24@gmail.com>
Date: Sun, 19 Jul 2020 21:24:19 +0200
Subject: chore: new algorithms

---
 I_anno/Programmazione_2/algorithms/log.cc  | 25 ++++++++++++++++++++
 I_anno/Programmazione_2/algorithms/pow.cc  | 34 ++++++++++++++++++++++++++
 I_anno/Programmazione_2/algorithms/sqrt.cc | 38 ++++++++++++++++++++++++++++++
 3 files changed, 97 insertions(+)
 create mode 100644 I_anno/Programmazione_2/algorithms/log.cc
 create mode 100644 I_anno/Programmazione_2/algorithms/pow.cc
 create mode 100644 I_anno/Programmazione_2/algorithms/sqrt.cc

(limited to 'I_anno/Programmazione_2')

diff --git a/I_anno/Programmazione_2/algorithms/log.cc b/I_anno/Programmazione_2/algorithms/log.cc
new file mode 100644
index 0000000..1e49a2e
--- /dev/null
+++ b/I_anno/Programmazione_2/algorithms/log.cc
@@ -0,0 +1,25 @@
+#include<iostream>
+
+using namespace std;
+
+double log(double n) {
+    if(n <= 2) return 1.0;
+    return 1.0 + log(n/2);
+}
+
+int log2(double n) {
+    int a = 1;
+
+    while(n > 2) {
+        n /= 2;
+        ++a;
+    }
+
+    return a;
+}
+
+int main() {
+    for(int i = 0; i < 25; ++i)
+        cout << i << ' ' << log(i) << ' ' << log2(i) << endl;
+    return 0;
+}
diff --git a/I_anno/Programmazione_2/algorithms/pow.cc b/I_anno/Programmazione_2/algorithms/pow.cc
new file mode 100644
index 0000000..70f5b43
--- /dev/null
+++ b/I_anno/Programmazione_2/algorithms/pow.cc
@@ -0,0 +1,34 @@
+#include<iostream>
+
+using namespace std;
+
+int pow(int b, int e) {
+    if(e == 0) return 1;
+    int a = b;
+    int inc = b;
+    for(int i = 0; i < e-1; ++i) {
+        for(int j = 0; j < b-1; ++j) {
+            a+=inc;
+        }
+        inc = a;
+    }
+    return a;
+}
+
+int mul(int b, int e) {
+    if(e == 0) return 0;
+
+    return b+mul(b, e-1);
+}
+
+int pow2(int b, int e) {
+    if(e == 0) return 1;
+
+    return mul(b, pow(b, e-1));
+}
+
+int main() {
+    cout << pow(2, 5) << endl;
+    cout << pow2(2, 5) << endl;
+    return 0;
+}
diff --git a/I_anno/Programmazione_2/algorithms/sqrt.cc b/I_anno/Programmazione_2/algorithms/sqrt.cc
new file mode 100644
index 0000000..01d1079
--- /dev/null
+++ b/I_anno/Programmazione_2/algorithms/sqrt.cc
@@ -0,0 +1,38 @@
+#include<iostream>
+
+using namespace std;
+
+double abs(double n) {
+    if(n < 0) return -n;
+
+    return n;
+}
+
+
+double sq(int n) {
+    double x = n;
+    double y = 1;
+    while(x-y > 0.0000001) {
+        x = (x+y)/2;
+        y = n/x;
+    }
+    return x;
+}
+
+double sq2_n(double n, double a) {
+    if(abs(a*a - n) <= 0.000001) {
+        return a;
+    }
+
+    return sq2_n(n, (a+n/a)/2);
+}
+
+double sq2(int n) {
+    return sq2_n(n, n/2);
+}
+
+int main() {
+    cout << sq(81) << endl;
+    cout << sq2(81) << endl;
+    return 0;
+}
-- 
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