+
+ Bank Requests
A solution to one of my coding interview questions. Complete solution - written in GoLang
+
+Task:
+You've been asked to program a bot for a popular bank that will automate the management of incoming requests. There are three types of requests the bank can receive:
+
+- transfer i j sum: request to transfer sum amount of money from the
i-th account to the j-th one
+- deposit
i sum: request to deposit sum amount of money in the i-th account
+- withdraw
i sum: request to withdraw sum amount of money from the i-th account.
+
+Your bot should also be able to process invalid requests. There are two types of invalid requests: invalid account number in the requests; deposit / withdrawal of a larger amount of money than is currently available.
+For the given list of accounts and requests, return the state of accounts after all requests have been processed, or an array of a single element [- ] (please note the minus sign), where is the 1-based index of the first invalid request.
+Example for accounts = [10, 100, 20, 50, 30] and requests = ["withdraw 2 10", "transfer 5 1 20", "deposit 5 20", "transfer 3 4 15"], the output should be bankRequests(accounts, requests) = [30, 90, 5, 65, 30].
+accounts = [10, 100, 20, 50, 30] : 代表 ID:1 有10元, ID:2 有100元 ...
+"withdraw 2 10" : 從ID:2 提領 10元, 所以100-10 最後得到accounts= [10, 90, 20, 50, 30]
+Here are the states of accounts after each request:
+
+"withdraw 2 10": [10, 90, 20, 50, 30]"transfer 5 1 20": [30, 90, 20, 50, 10]"deposit 5 20": [30, 90, 20, 50, 30]"transfer 3 4 15": [30, 90, 5, 65, 30], which is the answer
+For accounts = [20, 1000, 500, 40, 90] and requests = ["deposit 3 400", "transfer 1 2 30", "withdraw 4 50"], the output should be bankRequests(accounts, requests) = [-2].
+After the first request, accounts becomes equal to [20, 1000, 900, 40, 90], but the second one turns it into [-10, 1030, 900, 40, 90], which is invalid. Thus, the second request is invalid, and the answer is [-2]. Note that the last request is also invalid, but it shouldn't be included in the answer.
+中文意思:
+你被要求為一家知名銀行編寫一個機器人，該機器人將自動處理來自客戶的請求。銀行可能會收到三種類型的請求：
+
+transfer i j sum：從第i個帳戶轉移sum金額到第j個帳戶的請求deposit i sum：向第i個帳戶存入sum金額的請求withdraw i sum：從第i個帳戶提取sum金額的請求。
+你的機器人還應該能夠處理無效的請求。無效的請求有兩種類型：請求中的帳戶號碼無效；存款/提款金額大於當前可用金額。
+對於給定的帳戶列表和請求，返回處理完所有請求後的帳戶狀態，或單一元素為[- ]的數組（請注意負號），其中 是第一個無效請求的從1開始的索引。
+以accounts = [10, 100, 20, 50, 30] 和 requests = ["withdraw 2 10", "transfer 5 1 20", "deposit 5 20", "transfer 3 4 15"] 為例，輸出應為 bankRequests(accounts, requests) = [30, 90, 5, 65, 30]。
+accounts = [10, 100, 20, 50, 30] 代表：ID:1 有10元, ID:2 有100元 ...
+"withdraw 2 10" 從ID:2 提領 10元，所以100-10 最後得到accounts= [10, 90, 20, 50, 30]
+這是每個請求後帳戶的狀態：
+
+"withdraw 2 10": [10, 90, 20, 50, 30]"transfer 5 1 20": [30, 90, 20, 50, 10]"deposit 5 20": [30, 90, 20, 50, 30]"transfer 3 4 15": [30, 90, 5, 65, 30]，這是答案
+對於accounts = [20, 1000, 500, 40, 90] 和 requests = ["deposit 3 400", "transfer 1 2 30", "withdraw 4 50"]，輸出應為 bankRequests(accounts, requests) = [-2]。
+第一個請求後，帳戶變成 [20, 1000, 900, 40, 90]，但第二個請求將其變為 [-10, 1030, 900, 40, 90]，這是無效的。因此，第二個請求無效，答案為[-2]。請注意最後一個請求也是無效的，但不應包含在答案中。
+解答
+package bankrequests
+
+import (
+ "errors"
+ "fmt"
+ "regexp"
+ "strconv"
+ "strings"
+ "sync"
+)
+
+var (
+ errInvaldTransfer = errors.New("invalid transfer")
+ errInvaldWithdraw = errors.New("invalid withdraw")
+ errInvaldDeposit = errors.New("invalid deposit")
+ errUnknownAction = errors.New("unknown action")
+)
+
+var requestScheme = [][]string{
+ 3: {"action", "from", "amount"},
+ 4: {"action", "from", "to", "amount"},
+}
+
+type BankService interface {
+ getActionName() string
+ transfer() error
+ withdraw() error
+ deposit() error
+}
+
+type Bank struct {
+ BankService
+ action string
+ requestId int
+ from int
+ to int
+ amount int
+ balances []int
+ requestFailed bool
+ failedRequest []int
+
+ mutex sync.RWMutex
+}
+
+func (bank *Bank) getActionName() string {
+ return bank.action
+}
+
+func (bank *Bank) transfer() error {
+ bank.mutex.Lock()
+ defer bank.mutex.Unlock()
+
+ invalidAmout := bank.balances[bank.from-1] < bank.amount
+ invalidReceiver := len(bank.balances) < bank.to
+ if invalidAmout || invalidReceiver {
+ return errInvaldTransfer
+ }
+ bank.balances[bank.from-1] -= bank.amount
+ bank.balances[bank.to-1] += bank.amount
+ return nil
+}
+
+func (bank *Bank) withdraw() error {
+ bank.mutex.Lock()
+ defer bank.mutex.Unlock()
+
+ if bank.balances[bank.from-1] < bank.amount {
+ return errInvaldWithdraw
+ }
+ bank.balances[bank.from-1] -= bank.amount
+ return nil
+}
+
+func (bank *Bank) deposit() error {
+ bank.mutex.Lock()
+ defer bank.mutex.Unlock()
+
+ invalidAccount := len(bank.balances) < bank.from
+ if invalidAccount {
+ return errInvaldDeposit
+ }
+ bank.balances[bank.from-1] += bank.amount
+ return nil
+}
+
+func NewBank() *Bank {
+ return &Bank{}
+}
+
+// 錯誤處理: 回傳錯誤為
+// 單一元素為`[- ]`的數組（請注意負號）
+func (bank *Bank) failedAction() {
+ bank.mutex.Lock()
+ defer bank.mutex.Unlock()
+ failed := []int{-bank.requestId}
+
+ bank.balances = []int{}
+ bank.requestFailed = true
+ bank.failedRequest = failed
+}
+
+func (bank *Bank) Action() {
+ var requestErr error
+ action := bank.getActionName()
+ // fmt.Println("action:", action)
+
+ switch action {
+ case "transfer":
+ requestErr = bank.transfer()
+ case "withdraw":
+ requestErr = bank.withdraw()
+ case "deposit":
+ requestErr = bank.deposit()
+ default:
+ requestErr = errUnknownAction
+ }
+ if requestErr != nil {
+ fmt.Println("requestErr:", requestErr)
+ bank.failedAction()
+ }
+}
+
+func extractRequestParams(request string) map[string]interface{} {
+ res := map[string]interface{}{}
+ reqSlice := strToSlice(request)
+ fmt.Println("reqSlice:", reqSlice)
+
+ // len is 3: {"action", "from", "amount"},
+ // len is 4: {"action", "from", "to", "amount"},
+ scheme := requestScheme[len(reqSlice)]
+
+ for i, v := range scheme {
+ res[v] = reqSlice[i]
+ }
+ return res
+}
+
+func strToSlice(str string) []interface{} {
+ var res []interface{}
+ erp := strings.Fields(str)
+
+ re, err := regexp.Compile("[0-9]+")
+ if err != nil {
+ fmt.Println("Error compiling regex:", err)
+ return nil
+ }
+
+ for _, v := range erp {
+ if isNum := re.MatchString(v); isNum {
+ if n, _ := strconv.Atoi(v); n != 0 {
+ res = append(res, n)
+ }
+ } else {
+ res = append(res, v)
+ }
+ }
+
+ return res
+}
+
+func bankRequests(requests []string, balances []int) []int {
+ var res []int
+ for index, request := range requests {
+ reqParams := extractRequestParams(request)
+ bank := NewBank()
+ bank.requestId = index + 1
+ bank.action = reqParams["action"].(string)
+ bank.amount = reqParams["amount"].(int)
+ bank.from = reqParams["from"].(int)
+ if _, ok := reqParams["to"]; ok {
+ bank.to = reqParams["to"].(int)
+ }
+
+ bank.balances = balances
+ bank.Action()
+
+ if bank.requestFailed {
+ return bank.failedRequest
+ }
+ res = bank.balances
+ }
+ return res
+}
+
+unit test
+package bankrequests
+
+import (
+ "reflect"
+ "testing"
+)
+
+var tests = []struct {
+ arg1 []string
+ arg2 []int
+ want []int
+}{
+ {
+ []string{
+ "transfer 1 4 10",
+ "deposit 3 10",
+ "withdraw 5 15",
+ },
+ []int{20, 30, 10, 90, 60},
+ []int{10, 30, 20, 100, 45},
+ },
+ {
+ []string{
+ "transfer 1 4 40",
+ "deposit 3 10",
+ "withdraw 5 65",
+ },
+ []int{20, 30, 10, 90, 60},
+ []int{-1},
+ },
+ {
+ []string{
+ "withdraw 2 10",
+ "transfer 5 1 20",
+ "deposit 5 20",
+ "transfer 3 4 15",
+ },
+ []int{10, 100, 20, 50, 30},
+ []int{30, 90, 5, 65, 30},
+ },
+ {
+ []string{
+ "deposit 3 400",
+ "transfer 1 2 30",
+ "withdraw 4 50",
+ },
+ []int{20, 1000, 500, 40, 90},
+ []int{-2},
+ },
+}
+
+func TestBankRequests(t *testing.T) {
+ for _, tt := range tests {
+ if got := bankRequests(tt.arg1, tt.arg2); !reflect.DeepEqual(got, tt.want) {
+ t.Errorf("got = %v, want = %v", got, tt.want)
+ }
+ }
+}
+
+Reference
+
+
+
+ 
