From 649f0dc843b04fe90dc2c58596e1285d23b047ea Mon Sep 17 00:00:00 2001
From: Yohaan <yozaam@gmail.com>
Date: Fri, 23 Oct 2020 03:39:05 +0000
Subject: [PATCH] day 3 run length

---
 day3_reverse_no_inbuilt.py  | 21 ++++++++++++++++++
 day3_run_length_encoding.py | 36 ++++++++++++++++++++++++++++++
 main.py                     | 44 ++++++++++++++++++++++++++++---------
 3 files changed, 91 insertions(+), 10 deletions(-)
 create mode 100644 day3_reverse_no_inbuilt.py
 create mode 100644 day3_run_length_encoding.py

diff --git a/day3_reverse_no_inbuilt.py b/day3_reverse_no_inbuilt.py
new file mode 100644
index 0000000..2ca7f13
--- /dev/null
+++ b/day3_reverse_no_inbuilt.py
@@ -0,0 +1,21 @@
+# Required concepts: https://www.w3schools.com/python/python_intro.asp while loops and lists
+
+print('Question: Reverse a list without inbuilt function/slicing')
+
+li = [1,2,3,4,5]
+# we need to make the first element the last
+# and then keep swapping them :D
+left, right = 0, len(li)-1
+
+while left < right:
+  li[left],li[right] = li[right],li[left]
+  left +=1
+  right -=1
+
+#single line
+li = [1,2,3,4,5]
+for left in range(len(li)//2):
+  li[left],li[len(li)-left-1] = li[len(li)-left-1],li[left] 
+
+print('Answer:')
+print(li)
\ No newline at end of file
diff --git a/day3_run_length_encoding.py b/day3_run_length_encoding.py
new file mode 100644
index 0000000..186e199
--- /dev/null
+++ b/day3_run_length_encoding.py
@@ -0,0 +1,36 @@
+# Required concepts: https://www.w3schools.com/python/python_intro.asp loops and strings
+
+print('Question: Convert a string into its run length encoding, each char, followed by its consecutive frequency')
+
+string = 'aaabbbcccc'
+res = '' 
+# we want to encode as, val,consecutive fre
+# a3b3c4 is the desired output
+
+cur_freq = 0
+for i in range(len(string)-1):
+  if string[i] == string[i+1]:
+    cur_freq += 1
+  else:
+    res += string[i] + str(cur_freq)
+    cur_freq = 1
+res += string[-1] + str(cur_freq)
+
+print('Answer:')
+print(res)
+
+"""
+alternate easy method:
+cur_freq = 0
+cur_element = string[0]
+
+for element in string:
+  if element == cur_element:
+    cur_freq +=1 
+  else:
+    res += cur_element + str(cur_freq)
+    cur_freq = 1
+    cur_element = element
+
+res += cur_element + str(cur_freq)
+"""
\ No newline at end of file
diff --git a/main.py b/main.py
index 295f6bf..d325a9e 100644
--- a/main.py
+++ b/main.py
@@ -1,16 +1,40 @@
-# Required concepts: https://www.w3schools.com/python/python_intro.asp Everything till for loops
+# Required concepts: https://www.w3schools.com/python/python_intro.asp loops and strings
 
-print('Question: repeat every character twice')
+print('Question: Restore a string from its run length encoding, where each char, followed by its consecutive frequency')
 
-li = ['a' , 'b' , 'c' , 'd']
-# we want ['aa' , 'bb' , 'cc' , 'dd']
 
-for i in range(len(li)):
-  li[i]  = li[i]*2
-  # all elements repeat twice so *2
+string = 'a2b3c4'
+res = '' 
+# we want to encode as, val,consecutive fre
+# aaabbbcccc is the desired output
+
+for i in range(1,len(string),2):
+  # visit only digits ;) on odd indices
+  for _ in range(int(string[i])):
+    res += string[i-1]
+  # keep adding the prev character as many times as required
+
 
-#single line let's repeat them again
-result = [letter*2 for letter in li]
 print('Answer:')
-print(result)
+print(res)
+
+print('Question: Restore a string from its run length encoding, where each char, followed by its consecutive frequency (may be ≥1 digit)')
+# method if frequency is more than one digit!
+string = 'a2b3c11'
+res = '' 
 
+freq = 0
+cur_element = ''
+for i in range(len(string)):
+  # visit only digits ;) 
+  if string[i].isdigit():
+    freq = freq * 10 + int(string[i])
+  else:
+    res += cur_element * freq
+    freq = 0
+    cur_element = string[i]
+
+res += cur_element * freq
+
+print('Answer:')
+print(res)
\ No newline at end of file