Added tasks 638, 639, 640, 641

Author: ThanhNIT

README.md

@@ -1674,6 +1674,10 @@ implementation 'com.github.javadev:leetcode-in-kotlin:1.9'
 | 0763 |[Partition Labels](src/main/kotlin/g0701_0800/s0763_partition_labels/Solution.kt)| Medium | Top_100_Liked_Questions, String, Hash_Table, Greedy, Two_Pointers, Data_Structure_II_Day_7_String | 235 | 84.75
 | 0739 |[Daily Temperatures](src/main/kotlin/g0701_0800/s0739_daily_temperatures/Solution.kt)| Medium | Top_100_Liked_Questions, Array, Stack, Monotonic_Stack, Programming_Skills_II_Day_6 | 936 | 80.54
 | 0647 |[Palindromic Substrings](src/main/kotlin/g0601_0700/s0647_palindromic_substrings/Solution.kt)| Medium | Top_100_Liked_Questions, String, Dynamic_Programming | 266 | 67.83
+| 0641 |[Design Circular Deque](src/main/kotlin/g0601_0700/s0641_design_circular_deque/MyCircularDeque.kt)| Medium | Array, Design, Linked_List, Queue | 232 | 100.00
+| 0640 |[Solve the Equation](src/main/kotlin/g0601_0700/s0640_solve_the_equation/Solution.kt)| Medium | String, Math, Simulation | 170 | 66.67
+| 0639 |[Decode Ways II](src/main/kotlin/g0601_0700/s0639_decode_ways_ii/Solution.kt)| Hard | String, Dynamic_Programming | 259 | 100.00
+| 0638 |[Shopping Offers](src/main/kotlin/g0601_0700/s0638_shopping_offers/Solution.kt)| Medium | Array, Dynamic_Programming, Bit_Manipulation, Backtracking, Bitmask, Memoization | 195 | 100.00
 | 0637 |[Average of Levels in Binary Tree](src/main/kotlin/g0601_0700/s0637_average_of_levels_in_binary_tree/Solution.kt)| Easy | Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree | 249 | 100.00
 | 0636 |[Exclusive Time of Functions](src/main/kotlin/g0601_0700/s0636_exclusive_time_of_functions/Solution.kt)| Medium | Array, Stack | 270 | 80.00
 | 0633 |[Sum of Square Numbers](src/main/kotlin/g0601_0700/s0633_sum_of_square_numbers/Solution.kt)| Medium | Math, Binary_Search, Two_Pointers, Binary_Search_I_Day_10 | 126 | 100.00

src/main/kotlin/g0601_0700/s0638_shopping_offers/Solution.kt

@@ -0,0 +1,69 @@
+package g0601_0700.s0638_shopping_offers
+
+// #Medium #Array #Dynamic_Programming #Bit_Manipulation #Backtracking #Bitmask #Memoization
+// #2023_02_10_Time_195_ms_(100.00%)_Space_35.1_MB_(100.00%)
+
+class Solution() {
+    fun shoppingOffers(
+        price: List<Int>,
+        special: List<List<Int>>,
+        needs: List<Int>
+    ): Int {
+        val map: MutableMap<List<Int>, Int> = HashMap()
+        shoppingOffersUtil(price, special, needs, map)
+        return map[needs]!!
+    }
+
+    private fun shoppingOffersUtil(
+        price: List<Int>,
+        special: List<List<Int>>,
+        needs: List<Int>,
+        map: MutableMap<List<Int>, Int>
+    ): Int {
+        if (map.containsKey(needs)) {
+            return map[needs]!!
+        }
+        var ans = computePrice(price, needs)
+        for (i in special.indices) {
+            if (verify(special[i], needs)) {
+                ans = Math.min(
+                    special[i][needs.size] +
+                        shoppingOffersUtil(
+                            price,
+                            special,
+                            updatedNeeds(needs, special[i]),
+                            map
+                        ),
+                    ans
+                )
+            }
+        }
+        map[needs] = ans
+        return (map[needs])!!
+    }
+
+    private fun updatedNeeds(needs: List<Int>, special: List<Int>): List<Int> {
+        val updatedNeeds: MutableList<Int> = ArrayList(needs)
+        for (i in needs.indices) {
+            updatedNeeds[i] = updatedNeeds[i] - special[i]
+        }
+        return updatedNeeds
+    }
+
+    private fun verify(special: List<Int>, needs: List<Int>): Boolean {
+        for (i in needs.indices) {
+            if (special[i] > needs[i]) {
+                return false
+            }
+        }
+        return true
+    }
+
+    private fun computePrice(price: List<Int>, needs: List<Int>): Int {
+        var ans = 0
+        for (i in needs.indices) {
+            ans += (needs[i] * price[i])
+        }
+        return ans
+    }
+}

src/main/kotlin/g0601_0700/s0638_shopping_offers/readme.md

@@ -0,0 +1,46 @@
+638\. Shopping Offers
+
+Medium
+
+In LeetCode Store, there are `n` items to sell. Each item has a price. However, there are some special offers, and a special offer consists of one or more different kinds of items with a sale price.
+
+You are given an integer array `price` where `price[i]` is the price of the <code>i<sup>th</sup></code> item, and an integer array `needs` where `needs[i]` is the number of pieces of the <code>i<sup>th</sup></code> item you want to buy.
+
+You are also given an array `special` where `special[i]` is of size `n + 1` where `special[i][j]` is the number of pieces of the <code>j<sup>th</sup></code> item in the <code>i<sup>th</sup></code> offer and `special[i][n]` (i.e., the last integer in the array) is the price of the <code>i<sup>th</sup></code> offer.
+
+Return _the lowest price you have to pay for exactly certain items as given, where you could make optimal use of the special offers_. You are not allowed to buy more items than you want, even if that would lower the overall price. You could use any of the special offers as many times as you want.
+
+**Example 1:**
+
+**Input:** price = [2,5], special = [[3,0,5],[1,2,10]], needs = [3,2]
+
+**Output:** 14
+
+**Explanation:** There are two kinds of items, A and B. Their prices are $2 and $5 respectively. 
+
+In special offer 1, you can pay $5 for 3A and 0B In special offer 2, you can pay $10 for 1A and 2B. 
+
+You need to buy 3A and 2B, so you may pay $10 for 1A and 2B (special offer #2), and $4 for 2A.
+
+**Example 2:**
+
+**Input:** price = [2,3,4], special = [[1,1,0,4],[2,2,1,9]], needs = [1,2,1]
+
+**Output:** 11
+
+**Explanation:** The price of A is $2, and $3 for B, $4 for C.
+
+You may pay $4 for 1A and 1B, and $9 for 2A ,2B and 1C. 
+
+You need to buy 1A ,2B and 1C, so you may pay $4 for 1A and 1B (special offer #1), and $3 for 1B, $4 for 1C. 
+
+You cannot add more items, though only $9 for 2A ,2B and 1C.
+
+**Constraints:**
+
+*   `n == price.length == needs.length`
+*   `1 <= n <= 6`
+*   `0 <= price[i], needs[i] <= 10`
+*   `1 <= special.length <= 100`
+*   `special[i].length == n + 1`
+*   `0 <= special[i][j] <= 50`

src/main/kotlin/g0601_0700/s0639_decode_ways_ii/Solution.kt

@@ -0,0 +1,49 @@
+package g0601_0700.s0639_decode_ways_ii
+
+// #Hard #String #Dynamic_Programming #2023_02_10_Time_259_ms_(100.00%)_Space_38.4_MB_(100.00%)
+
+class Solution {
+    fun numDecodings(s: String): Int {
+        if (s[0] == '0') {
+            return 0
+        }
+        val dp = LongArray(s.length + 1)
+        dp[0] = 1
+        dp[1] = (if (s[0] == '*') 9 else 1).toLong()
+        val ch = s.toCharArray()
+        for (i in 2..ch.size) {
+            if (ch[i - 1] == '0') {
+                if (ch[i - 2] == '1' || ch[i - 2] == '2') {
+                    dp[i] = dp[i - 2]
+                } else if (ch[i - 2] == '*') {
+                    dp[i] = 2 * dp[i - 2]
+                } else {
+                    return 0
+                }
+            } else if (ch[i - 1] >= '1' && ch[i - 1] <= '6') {
+                dp[i] = dp[i - 1]
+                if (ch[i - 2] == '1' || ch[i - 2] == '2') {
+                    dp[i] += dp[i - 2]
+                } else if (ch[i - 2] == '*') {
+                    dp[i] += 2 * dp[i - 2]
+                }
+            } else if (ch[i - 1] >= '7' && ch[i - 1] <= '9') {
+                dp[i] = dp[i - 1]
+                if (ch[i - 2] == '1' || ch[i - 2] == '*') {
+                    dp[i] += dp[i - 2]
+                }
+            } else if (ch[i - 1] == '*') {
+                dp[i] = 9 * dp[i - 1]
+                if (ch[i - 2] == '1') {
+                    dp[i] += 9 * dp[i - 2]
+                } else if (ch[i - 2] == '2') {
+                    dp[i] += 6 * dp[i - 2]
+                } else if (ch[i - 2] == '*') {
+                    dp[i] += 15 * dp[i - 2]
+                }
+            }
+            dp[i] = dp[i] % 1000000007
+        }
+        return dp[s.length].toInt()
+    }
+}

src/main/kotlin/g0601_0700/s0639_decode_ways_ii/readme.md

@@ -0,0 +1,49 @@
+639\. Decode Ways II
+
+Hard
+
+A message containing letters from `A-Z` can be **encoded** into numbers using the following mapping:
+
+'A' -> "1" 'B' -> "2" ... 'Z' -> "26"
+
+To **decode** an encoded message, all the digits must be grouped then mapped back into letters using the reverse of the mapping above (there may be multiple ways). For example, `"11106"` can be mapped into:
+
+*   `"AAJF"` with the grouping `(1 1 10 6)`
+*   `"KJF"` with the grouping `(11 10 6)`
+
+Note that the grouping `(1 11 06)` is invalid because `"06"` cannot be mapped into `'F'` since `"6"` is different from `"06"`.
+
+**In addition** to the mapping above, an encoded message may contain the `'*'` character, which can represent any digit from `'1'` to `'9'` (`'0'` is excluded). For example, the encoded message `"1*"` may represent any of the encoded messages `"11"`, `"12"`, `"13"`, `"14"`, `"15"`, `"16"`, `"17"`, `"18"`, or `"19"`. Decoding `"1*"` is equivalent to decoding **any** of the encoded messages it can represent.
+
+Given a string `s` consisting of digits and `'*'` characters, return _the **number** of ways to **decode** it_.
+
+Since the answer may be very large, return it **modulo** <code>10<sup>9</sup> + 7</code>.
+
+**Example 1:**
+
+**Input:** s = "\*"
+
+**Output:** 9
+
+**Explanation:** The encoded message can represent any of the encoded messages "1", "2", "3", "4", "5", "6", "7", "8", or "9". Each of these can be decoded to the strings "A", "B", "C", "D", "E", "F", "G", "H", and "I" respectively. Hence, there are a total of 9 ways to decode "\*".
+
+**Example 2:**
+
+**Input:** s = "1\*"
+
+**Output:** 18
+
+**Explanation:** The encoded message can represent any of the encoded messages "11", "12", "13", "14", "15", "16", "17", "18", or "19". Each of these encoded messages have 2 ways to be decoded (e.g. "11" can be decoded to "AA" or "K"). Hence, there are a total of 9 \* 2 = 18 ways to decode "1\*".
+
+**Example 3:**
+
+**Input:** s = "2\*"
+
+**Output:** 15
+
+**Explanation:** The encoded message can represent any of the encoded messages "21", "22", "23", "24", "25", "26", "27", "28", or "29". "21", "22", "23", "24", "25", and "26" have 2 ways of being decoded, but "27", "28", and "29" only have 1 way. Hence, there are a total of (6 \* 2) + (3 \* 1) = 12 + 3 = 15 ways to decode "2\*".
+
+**Constraints:**
+
+*   <code>1 <= s.length <= 10<sup>5</sup></code>
+*   `s[i]` is a digit or `'*'`.

src/main/kotlin/g0601_0700/s0640_solve_the_equation/Solution.kt

@@ -0,0 +1,68 @@
+package g0601_0700.s0640_solve_the_equation
+
+// #Medium #String #Math #Simulation #2023_02_10_Time_170_ms_(66.67%)_Space_35.3_MB_(66.67%)
+
+class Solution {
+    fun solveEquation(equation: String): String {
+        val eqs = equation.split("=".toRegex()).dropLastWhile { it.isEmpty() }.toTypedArray()
+        val arr1 = evaluate(eqs[0])
+        val arr2 = evaluate(eqs[1])
+        return if (arr1[0] == arr2[0] && arr1[1] == arr2[1]) {
+            "Infinite solutions"
+        } else if (arr1[0] == arr2[0]) {
+            "No solution"
+        } else {
+            "x=" + (arr2[1] - arr1[1]) / (arr1[0] - arr2[0])
+        }
+    }
+
+    private fun evaluate(eq: String): IntArray {
+        val arr = eq.toCharArray()
+        var f = false
+        var a = 0
+        var b = 0
+        var i = 0
+        if (arr[0] == '-') {
+            f = true
+            i++
+        }
+        while (i < arr.size) {
+            if (arr[i] == '-') {
+                f = true
+                i++
+            } else if (arr[i] == '+') {
+                i++
+            }
+            val sb = StringBuilder()
+            while (i < arr.size && Character.isDigit(arr[i])) {
+                sb.append(arr[i])
+                i++
+            }
+            val n = sb.toString()
+            if (i < arr.size && arr[i] == 'x') {
+                var number: Int
+                number = if (n == "") {
+                    1
+                } else {
+                    n.toInt()
+                }
+                if (f) {
+                    number = -number
+                }
+                a += number
+                i++
+            } else {
+                var number = n.toInt()
+                if (f) {
+                    number = -number
+                }
+                b += number
+            }
+            f = false
+        }
+        val op = IntArray(2)
+        op[0] = a
+        op[1] = b
+        return op
+    }
+}

src/main/kotlin/g0601_0700/s0640_solve_the_equation/readme.md

@@ -0,0 +1,31 @@
+640\. Solve the Equation
+
+Medium
+
+Solve a given equation and return the value of `'x'` in the form of a string `"x=#value"`. The equation contains only `'+'`, `'-'` operation, the variable `'x'` and its coefficient. You should return `"No solution"` if there is no solution for the equation, or `"Infinite solutions"` if there are infinite solutions for the equation.
+
+If there is exactly one solution for the equation, we ensure that the value of `'x'` is an integer.
+
+**Example 1:**
+
+**Input:** equation = "x+5-3+x=6+x-2"
+
+**Output:** "x=2"
+
+**Example 2:**
+
+**Input:** equation = "x=x"
+
+**Output:** "Infinite solutions"
+
+**Example 3:**
+
+**Input:** equation = "2x=x"
+
+**Output:** "x=0"
+
+**Constraints:**
+
+*   `3 <= equation.length <= 1000`
+*   `equation` has exactly one `'='`.
+*   `equation` consists of integers with an absolute value in the range `[0, 100]` without any leading zeros, and the variable `'x'`.