Integer factorization

Makefile

@@ -26,6 +26,11 @@ run:
 	@for dir in $(SUBDIRS); do \
 		echo "=== Running $$dir ==="; \
 		(cd $$dir && $(MAKE) SANITIZE=$(SANITIZE) run) || exit 1; \
+		## Run tests if present and fail the test if tests fail \
+		if [ -f "$$dir/tests.sh" ]; then \
+			echo "=== Running tests in $$dir ==="; \
+			(cd $$dir && ./tests.sh) || exit 1; \
+		fi; \
 	done
 
 # --------------------------

README.md

@@ -26,6 +26,8 @@ Examples include (and will expand to):
 * Parallelism
     * [parallel-transform](./parallel-transform/)
 * Performance‑oriented C++ idioms
+* Algorithms
+    * [integer-factorization](./integer-factorization/)
 
 ---
 
@@ -171,7 +173,7 @@ The CI setup requires **no updates** when new example folders are added.
 The CI will perform:
 1. `./clang-check.sh *.cpp *.hpp`
 2. `make SANITIZE=[address, thread, undefined]`
-3. `make run`
+3. `make run` which will run `make run` for each project and `./tests.sh` if it is present.
 
 ---
 

fold-left-fold-right/Makefile

@@ -5,7 +5,7 @@ include ../common.mk
 # CXXFLAGS += -pthread
 
 TARGET := $(notdir $(CURDIR))
-SRCS   := main.cpp
+SRCS   := $(wildcard *.cpp)
 OBJS   := $(SRCS:.cpp=.o)
 
 all: $(TARGET)

integer-factorization/Makefile

@@ -0,0 +1,31 @@
+# pull in shared compiler settings
+include ../common.mk
+
+# per-example flags
+# CXXFLAGS += -pthread
+
+## get it from the folder name
+TARGET := $(notdir $(CURDIR))
+## all *.cpp files in this folder
+SRCS   := $(wildcard *.cpp)
+OBJS   := $(SRCS:.cpp=.o)
+
+all: $(TARGET)
+
+$(TARGET): $(OBJS)
+	$(CXX) $(CXXFLAGS) -o $@ $^
+
+%.o: %.cpp
+	$(CXX) $(CXXFLAGS) -c $< -o $@
+
+run: $(TARGET)
+	./$(TARGET) $(ARGS)
+
+clean:
+	rm -f $(OBJS) $(TARGET)
+
+# Delegates to top-level Makefile
+check-format:
+	$(MAKE) -f ../Makefile check-format DIR=$(CURDIR)
+
+.PHONY: all clean run check-format

integer-factorization/factorization_algorithms.cpp

@@ -0,0 +1,17 @@
+#include "factorization_algorithms.hpp"
+
+std::vector<long long>
+trial_division(long long n)
+{
+    std::vector<long long> factors;
+    for (long long i = 2; i * i <= n; ++i) {
+        while (n % i == 0) {
+            factors.push_back(i);
+            n /= i;
+        }
+    }
+    if (n > 1) {
+        factors.push_back(n);
+    }
+    return factors;
+}

integer-factorization/factorization_algorithms.hpp

@@ -0,0 +1,13 @@
+/**
+ * This header file declares the function prototypes for various integer factorization algorithms.
+ */
+
+#ifndef FACTORIZATION_ALGORITHMS_H
+#define FACTORIZATION_ALGORITHMS_H
+
+#include <vector>
+
+std::vector<long long>
+trial_division(long long n);
+
+#endif // FACTORIZATION_ALGORITHMS_H

integer-factorization/main.cpp

@@ -0,0 +1,98 @@
+/**
+ * This program implements various algorithms for integer factorization,
+ * It takes integer(s) from the command line or a file and outputs their prime
+ * factorizations.
+ *
+ * Usage:
+ *   ./integer-factorization [options] [integers...]
+ * Options:
+ *   -h, --help          Show this help message and exit
+ *   -f, --file FILE     Read integers from FILE, one per line
+ *   -o, --output FILE    Write output to FILE instead of stdout
+ */
+
+#include <iostream>
+#include <fstream>
+#include <vector>
+#include <string>
+#include <getopt.h>
+#include "factorization_algorithms.hpp"
+
+void
+print_help()
+{
+    std::cout << "Usage: ./integer-factorization [options] [integers...]\n"
+              << "Options:\n"
+              << "  -h, --help          Show this help message and exit\n"
+              << "  -f, --file FILE     Read integers from FILE, one per line\n"
+              << "  -o, --output FILE    Write output to FILE instead of stdout\n";
+}
+
+int
+main(int argc, char* argv[])
+{
+    std::string input_file;
+    std::string output_file;
+    std::vector<long long> numbers;
+
+    static struct option long_options[] = {
+        {"help", no_argument, 0, 'h'},
+        {"file", required_argument, 0, 'f'},
+        {"output", required_argument, 0, 'o'},
+        {0, 0, 0, 0}};
+
+    int opt;
+    while ((opt = getopt_long(argc, argv, "hf:o:", long_options, NULL)) != -1) {
+        switch (opt) {
+        case 'h':
+            print_help();
+            return 0;
+        case 'f':
+            input_file = optarg;
+            break;
+        case 'o':
+            output_file = optarg;
+            break;
+        default:
+            print_help();
+            return 1;
+        }
+    }
+
+    // Read numbers from file if specified
+    if (!input_file.empty()) {
+        std::ifstream infile(input_file);
+        long long num;
+        while (infile >> num) {
+            numbers.push_back(num);
+        }
+    }
+
+    // Read numbers from command line arguments
+    for (int index = optind; index < argc; index++) {
+        numbers.push_back(std::stoll(argv[index]));
+    }
+
+    // Prepare output stream
+    std::ostream* out_stream = &std::cout;
+    std::ofstream outfile;
+    if (!output_file.empty()) {
+        outfile.open(output_file);
+        out_stream = &outfile;
+    }
+
+    // Factor each number and output the result
+    for (const auto& number : numbers) {
+        std::vector<long long> factors;
+        factors = trial_division(number);
+        *out_stream << "Factors of " << number << ": ";
+        for (const auto& factor : factors) {
+            *out_stream << factor << " ";
+        }
+        *out_stream << "\n";
+    }
+    if (outfile.is_open()) {
+        outfile.close();
+    }
+    return 0;
+}

integer-factorization/tests.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+set -ex
+
+./integer-factorization -h
+
+./integer-factorization 1234 45678

parallel-transform/Makefile

@@ -6,7 +6,7 @@ include ../common.mk
 
 ## get it from the folder name
 TARGET := $(notdir $(CURDIR))
-SRCS   := main.cpp
+SRCS   := $(wildcard *.cpp)
 OBJS   := $(SRCS:.cpp=.o)
 
 all: $(TARGET)

smart-ptr/Makefile

@@ -4,18 +4,27 @@ include ../common.mk
 # per-example flags
 # CXXFLAGS += -pthread
 
+## get it from the folder name
 TARGET := $(notdir $(CURDIR))
-SRCS = main.cpp
+SRCS   := $(wildcard *.cpp)
+OBJS   := $(SRCS:.cpp=.o)
 
 all: $(TARGET)
 
-$(TARGET): $(SRCS)
-	$(CXX) $(CXXFLAGS) -o $(TARGET) $(SRCS)
+$(TARGET): $(OBJS)
+	$(CXX) $(CXXFLAGS) -o $@ $^
+
+%.o: %.cpp
+	$(CXX) $(CXXFLAGS) -c $< -o $@
 
 run: $(TARGET)
 	./$(TARGET) $(ARGS)
 
 clean:
-	rm -f $(TARGET)
+	rm -f $(OBJS) $(TARGET)
+
+# Delegates to top-level Makefile
+check-format:
+	$(MAKE) -f ../Makefile check-format DIR=$(CURDIR)
 
-.PHONY: all clean
+.PHONY: all clean run check-format

thread-safe-queue/Makefile

@@ -5,7 +5,7 @@ include ../common.mk
 CXXFLAGS += -pthread
 
 TARGET := $(notdir $(CURDIR))
-SRCS   := main.cpp
+SRCS   := $(wildcard *.cpp)
 OBJS   := $(SRCS:.cpp=.o)
 
 all: $(TARGET)

unique-ptr-basics/Makefile

@@ -5,7 +5,7 @@ include ../common.mk
 # CXXFLAGS += -pthread
 
 TARGET := $(notdir $(CURDIR))
-SRCS   := main.cpp
+SRCS   := $(wildcard *.cpp)
 OBJS   := $(SRCS:.cpp=.o)
 
 all: $(TARGET)

views-zip-enumerate/Makefile

@@ -5,7 +5,7 @@ include ../common.mk
 # CXXFLAGS += -pthread
 
 TARGET := $(notdir $(CURDIR))
-SRCS   := main.cpp
+SRCS   := $(wildcard *.cpp)
 OBJS   := $(SRCS:.cpp=.o)
 
 all: $(TARGET)