84, 134

084-solve.dfy

@@ -0,0 +1,16 @@
+method solve(n: nat) returns (r: nat)
+  ensures r == popcount(n)
+{
+  var m := n;
+  r := 0;
+  while m > 0 
+    invariant r + popcount(m) == popcount(n)
+  {
+    r := r + m % 2;
+    m := m / 2;
+  }
+}
+
+function popcount(n: nat): nat {
+  if n == 0 then 0 else n % 2 + popcount(n / 2)
+}

134-check_if_last_char_is_a_letter.dfy

@@ -0,0 +1,10 @@
+method check_if_last_char_is_a_letter(s: string) returns (b: bool)
+  ensures b <==> |s| > 0 && is_alpha(s[|s| - 1]) && (|s| == 1 || s[|s| - 2] == ' ')
+{
+  b := |s| > 0 && is_alpha(s[|s| - 1]) && (|s| == 1 || s[|s| - 2] == ' ');
+}
+
+
+predicate is_alpha(c: char) {
+    'a' <= c <= 'z' || 'A' <= c <= 'Z'
+}

README.md

@@ -86,7 +86,7 @@ Current status:
 - [x] 81. numerical_letter_grade
 - [x] 82. prime_length
 - [x] 83. starts_one_ends
-- [ ] 84. solve
+- [x] 84. solve
 - [x] 85. add
 - [ ] 86. anti_shuffle - complex strings
 - [ ] 87. get_row - sorting
@@ -136,7 +136,7 @@ Current status:
 - [ ] 131. digits
 - [ ] 132. is_nested
 - [x] 133. sum_squares
-- [ ] 134. check_if_last_char_is_a_letter
+- [x] 134. check_if_last_char_is_a_letter
 - [x] 135. can_arrange
 - [x] 136. largest_smallest_integers
 - [ ] 137. compare_one - ill-typed

REMAINING.md

@@ -5,6 +5,7 @@ Current status:
 ## Priority
 - [ ] 25. factorize
 - [ ] 36. fizz_buzz
+- [ ] 147. get_max_triples
 
 ## Other
 
@@ -14,7 +15,6 @@ Current status:
 - [ ] 47. median
 - [ ] 65. circular_shift
 - [ ] 79. decimal_to_binary
-- [ ] 84. solve
 - [ ] 90. next_smallest - nullable
 - [ ] 103. rounded_avg
 - [ ] 107. even_odd_palindrome
@@ -25,10 +25,7 @@ Current status:
 - [ ] 129. minPath
 - [ ] 131. digits
 - [ ] 132. is_nested
-- [ ] 134. check_if_last_char_is_a_letter
 - [ ] 141. file_name_check
-- [ ] 144. simplify
-- [ ] 147. get_max_triples
 - [ ] 156. int_to_mini_roman
 - [ ] 161. solve
 - [ ] 162. string_to_md5 - needs hash
@@ -50,6 +47,7 @@ Current status:
 - [ ] 117. select_words
 - [ ] 125. split_words
 - [ ] 140. fix_spaces
+- [ ] 144. simplify
 - [ ] 143. words_in_sentence
 - [ ] 160. do_algebra