Add bank_account_using_mutex_locks

Author: lisajulia

.gitignore

@@ -1 +1,2 @@
 assemble_teams_using_latch
+bank_account_using_mutex_locks

Makefile

@@ -5,10 +5,14 @@ SRC = $(wildcard *.cc)
 BIN = $(SRC:.cc=)
 
 # Rules
-default: assemble_teams_using_latch 
+default: assemble_teams_using_latch bank_account_using_mutex_locks
 
 assemble_teams_using_latch: assemble_teams_using_latch.cc
 	$(CXX) $(CXXFLAGS) -o assemble_teams_using_latch assemble_teams_using_latch.cc
+
+bank_account_using_mutex_locks: bank_account_using_mutex_locks.cc
+	$(CXX) $(CXXFLAGS) -o bank_account_using_mutex_locks bank_account_using_mutex_locks.cc
+
 clean:
 	@$(RM) $(BIN)
 

bank_account_using_mutex_locks.cc

@@ -0,0 +1,31 @@
+#include <iostream>
+#include <thread>
+#include <mutex>
+
+std::mutex accountMutex;
+int balance = 500;
+
+void withdraw(int amount, const std::string& user) {
+    std::unique_lock<std::mutex> lock(accountMutex, std::defer_lock);
+
+    // Check balance before locking
+    if (balance >= amount) {
+        // Lock now, after condition is checked
+        lock.lock();
+        balance -= amount;
+        std::cout << user << " successfully withdrew $" << amount << ". Remaining balance: $" << balance << std::endl;
+        lock.unlock(); // Can unlock manually
+    } else {
+        std::cout << user << " attempted to withdraw $" << amount << ", but insufficient funds." << std::endl;
+    }
+}
+
+int main() {
+    std::thread userA(withdraw, 100, "User A");
+    std::thread userB(withdraw, 100, "User B");
+
+    userA.join();
+    userB.join();
+    
+    return 0;
+}