August

0401-0500/0410_split_array_largest_sum.rb

@@ -0,0 +1,40 @@
+# @param {Integer[]} nums
+# @param {Integer} k
+# @return {Integer}
+def split_array(nums, k)
+ # count number of sub-array that has sum <= largest-sum
+ count_sub_arrs = lambda { |largest_sum|
+ count = 0
+ sum = 0
+ nums.each { |num|
+ if sum + num <= largest_sum
+ sum += num
+ else
+ count += 1
+ sum = num
+ end
+ }
+
+ count
+ }
+
+ # the smaller the largest-sum is, the more sub-arrays we can divide
+ # so we need to find the max largest-sum that we can divide nums into more than or equal k sub-arrays
+ # that is also the min largest-sum we can divide nums into k sub-arrays
+
+ low = nums.max
+ high = nums.sum + 1
+
+ while low < high
+ mid = (low + high)/2
+ count = count_sub_arrs.call(mid)
+
+ if count >= k # still be able to divide nums more than k sub-arrays
+ low = mid + 1
+ else
+ high = mid
+ end
+ end
+
+ low
+end

0401-0500/0447_number_of_boomerangs.rb

@@ -0,0 +1,18 @@
+# @param {Integer[][]} points
+# @return {Integer}
+def number_of_boomerangs(points)
+ count = 0
+ (0...points.length).each { |i|
+ dist_counter = Hash.new(0)
+ (0...points.length).each { |j|
+ dist = (points[i][0] - points[j][0])**2 + (points[i][1] - points[j][1])**2
+ # for each new boomerang point j, there're 2 boomerangs combine by j and each previous boomerang points
+ count += 2 * dist_counter[dist]
+ dist_counter[dist] += 1
+ }
+ # we also can count boomerangs each i by sum of Permutation(k, 2)
+ # count += dist_counter.values.reduce(0) { |sum, k| sum += k*(k-1) }
+ }
+
+ count
+end

0501-0600/0532_k_diff_pairs_in_an_array.rb

@@ -0,0 +1,20 @@
+# @param {Integer[]} nums
+# @param {Integer} k
+# @return {Integer}
+def find_pairs(nums, k)
+ count = 0
+ appear = Hash.new(0)
+
+ nums.each { |num|
+ next if appear[num] >= (k == 0 ? 2 : 1)
+
+ if k == 0
+ count += appear[num] == 1 ? 1 : 0
+ else
+ count += (appear[num-k] >= 1 ? 1 : 0) + (appear[num+k] >= 1 ? 1 : 0)
+ end
+ appear[num] += 1
+ }
+
+ count
+end

0501-0600/0551_student_attendance_record_i.rb

@@ -0,0 +1,23 @@
+# @param {String} s
+# @return {Boolean}
+def check_record(s)
+ a_count = 0
+ l_count = 0
+ l_prev = -1
+ (0...s.length).each { |i|
+ if s[i] == 'A'
+ a_count += 1
+ return false if a_count >= 2
+ elsif s[i] == 'L'
+ if l_prev == i - 1
+ l_count += 1
+ return false if l_count >= 3
+ else
+ l_count = 1
+ end
+ l_prev = i
+ end
+ }
+
+ true
+end

0601-0700/0640_solve_the_equation.rb

@@ -0,0 +1,45 @@
+# @param {String} equation
+# @return {String}
+def solve_equation(equation)
+ # summary: ax + b
+ count_x = lambda { |str|
+ a = 0
+ b = 0
+ num = nil
+ sign = 1
+ str.each_char { |c|
+ if c == 'x'
+ a += sign * (num || 1)
+ num = 0
+ elsif c == '+'
+ b += sign * num.to_i
+ num = nil
+ sign = 1
+ elsif c == '-'
+ b += sign * num.to_i
+ num = nil
+ sign = -1
+ else
+ num = (num || 0) * 10 + c.to_i
+ end
+ }
+ b += sign * num.to_i
+
+ return [a, b]
+ }
+
+ left, right = equation.split('=')
+ al, bl = count_x.call(left)
+ ar, br = count_x.call(right)
+
+ a = al - ar
+ b = br - bl
+
+ if a == 0
+ b == 0 ? "Infinite solutions" : "No solution"
+ elsif b % a != 0
+ "No solution"
+ else 
+ "x=#{b/a}"
+ end
+end

0801-0900/0811_subdomain_visit_count.rb

@@ -0,0 +1,22 @@
+# @param {String[]} cpdomains
+# @return {String[]}
+def subdomain_visits(cpdomains)
+ counter = Hash.new(0)
+ cpdomains.each { |cp|
+ count, domain = cp.split(' ')
+ count = count.to_i
+
+ i = domain.length
+ loop do
+ i = domain.rindex('.', i-1)
+ break if i.nil?
+
+ counter[domain[i+1..]] += count
+ end
+ counter[domain] += count
+ }
+
+ counter.map { |domain, count|
+ "#{count} #{domain}"
+ }
+end

1101-1200/1170_compare_strings_by_frequency_of_the_smallest_character.rb

@@ -0,0 +1,32 @@
+# @param {String[]} queries
+# @param {String[]} words
+# @return {Integer[]}
+def num_smaller_by_frequency(queries, words)
+ f = lambda { |str|
+ count = 0
+ curr = 'z'
+ str.each_char { |c|
+ if curr == c
+ count += 1
+ elsif curr.ord > c.ord
+ curr = c
+ count = 1
+ end
+ }
+ count
+ }
+
+ word_sorted = words.map { |word| f.call(word) }.sort
+
+ ans = []
+ queries.each { |q|
+ freq = f.call(q)
+ if i = word_sorted.bsearch_index { |w_freq| w_freq > freq }
+ ans << (word_sorted.length - i)
+ else
+ ans << 0
+ end
+ }
+
+ ans
+end

2101-2200/2134_minimum_swaps_to_group_all_1s_together_ii.rb

@@ -0,0 +1,21 @@
+# @param {Integer[]} nums
+# @return {Integer}
+def min_swaps(nums)
+ # sliding-window size = total ones
+ total_ones = nums.count { |num| num == 1 }
+ # circular
+ nums += nums
+ # number of swaps = number of zeros
+ zeros = 0
+ (0...total_ones).each { |i|
+ zeros += (nums[i] == 0 ? 1 : 0)
+ }
+ min = zeros
+
+ (total_ones...nums.length).each { |i|
+ zeros += (nums[i] == 0 ? 1 : 0) - (nums[i-total_ones] == 0 ? 1 : 0)
+ min = [min, zeros].min
+ }
+
+ min
+end

2601-2700/2678_number_of_senior_citizens.rb

@@ -0,0 +1,5 @@
+# @param {String[]} details
+# @return {Integer}
+def count_seniors(details)
+ details.count { |d| d[-4..-3].to_i > 60 }
+end

3201-3300/3217_delete_nodes_from-linked_list_present_in_array.rb

@@ -0,0 +1,30 @@
+# Definition for singly-linked list.
+# class ListNode
+# attr_accessor :val, :next
+# def initialize(val = 0, _next = nil)
+# @val = val
+# @next = _next
+# end
+# end
+# @param {Integer[]} nums
+# @param {ListNode} head
+# @return {ListNode}
+def modified_list(nums, head)
+ nums_hash = {}
+ nums.each { |num| nums_hash[num] = true }
+
+ head = head.next while nums_hash.has_key?(head.val)
+
+ prev_node = head
+ node = head.next
+ until node.nil?
+ unless nums_hash.has_key?(node.val)
+ prev_node.next = node
+ prev_node = node
+ end
+ node = node.next 
+ end
+ prev_node.next = node
+
+ head
+end