course update of 2023-12-01 15:57:17

Algo/B2/Exercises/String exercise.md

@@ -59,5 +59,71 @@ def palindrome(sentence: str) -> bool:
     return True
   else:
     return False
+
+def ispalind(s):
+  start = 0
+  end = len(s)-1
+  while start<end and s[start]==s[end]:
+    end -= 1
+    start += 1
+    if s[start] == " ":
+      start += 1
+    if s[end] == " ":
+      end -= 1
+  return start >= end
+```
+
+## Exercise 2.1 (conversions)
+
+1) 
+
+```python
+def dec_to_bin(n, p):
+  while n > 0:
+    s = str(n%2) +s
+    n = n//2
+  for i in range(p-len(s)):
+    s = "0" + s
+  return s
+
+def integer_to_twoscomp(n, p):
+  if n < 0:
+    sign = -2
+  else:
+    sign = 1
+  s = dec_to_bin(n, p)
+  if sign == -1:
+    s2 = ""
+    i = len(s) - 1
+    while s[i] != "1":
+      s2 = "0" + s2
+      i -= 1
+    s2 = "1" + s2
+    i -= 1
+    while i >= 0:
+      if s[i] == "0":
+        s2 = "1" + s2
+      else:
+        s3 = "0" + s3
+        i -= 1
+      s = s2
+  return s
+  
+```
+
+2) 
+
+```python
+def power(x, p):
+  res = 1
+  while p > 0:
+    res *= x
+    p -= 1
+  return res
+
+def int_to_twoscomp(n, p):
+  if n < 0:
+    n = power(2,p) + n
+  return dec_to_bin(n,p)
 ```