Makefile

# Competitive Programming Archive - build and run one solution.
#
#   make run   F=codeforces/1122/A          compile, then feed A.in on stdin
#   make build F=codeforces/1122/A          compile only
#   make run   F=codeforces/1122/A SAN=1    same, with address/UB sanitizers
#   make run   F=codeforces/1122/A STD=c++17  build against another standard
#   make clean                              remove the build/ tree
#
# F is a path relative to this file, with or without the .cpp suffix.
# When the sibling .in is missing the program reads your terminal instead.

# Matches the "GNU G++23" option on Codeforces. Override per-run: STD=c++17
STD      ?= c++23
CXXFLAGS := -std=$(STD) -O2 -Wall -Wextra -Wshadow

# Each flag combination gets its own tree. Make compares timestamps, not flags,
# so a shared directory would hand back a binary built with the other settings.
ifeq ($(SAN),1)
CXXFLAGS += -g -fsanitize=address,undefined -fno-omit-frame-pointer
BUILDDIR := build/$(STD)-san
else
BUILDDIR := build/$(STD)
endif

# Codeforces builds with real GCC, and Apple clang has no <bits/stdc++.h>, so
# only Homebrew's versioned g++ counts. Override with `make GXX=/path/to/g++`.
GXX := $(shell for v in 20 19 18 17 16 15 14 13 12; do command -v g++-$$v && break; done)

.DEFAULT_GOAL := help
.PHONY: help clean build run require-gcc

help:
	@echo 'usage:'
	@echo '  make run   F=codeforces/1122/A        compile, then run against A.in'
	@echo '  make build F=codeforces/1122/A        compile only'
	@echo '  make run   F=codeforces/1122/A SAN=1  add address/UB sanitizers'
	@echo '  make run   F=codeforces/1122/A STD=c++17  pick another standard'
	@echo '  make clean                            remove the build/ tree'
	@echo ''
	@echo "compiler: $(if $(GXX),$(GXX),none found - run 'brew install gcc')"

require-gcc:
	@if [ -z "$(GXX)" ]; then \
	  echo 'error: no Homebrew GCC found (looked for g++-12 .. g++-20).' >&2; \
	  echo 'Codeforces builds with real GCC, and Apple clang has no <bits/stdc++.h>.' >&2; \
	  echo '' >&2; \
	  echo '    brew install gcc' >&2; \
	  echo '' >&2; \
	  exit 1; \
	fi

ifeq ($(strip $(F)),)

build run:
	@echo 'error: set F to the solution path, e.g.' >&2
	@echo "    make $@ F=codeforces/1122/A" >&2
	@exit 1

else

STEM := $(patsubst %.cpp,%,$(F))
BIN  := $(BUILDDIR)/$(STEM)
IN   := $(STEM).in

build: $(BIN)

run: $(BIN)
	@if [ -f '$(IN)' ]; then \
	  echo '--- $(BIN) < $(IN) ---'; \
	  '$(BIN)' < '$(IN)'; \
	else \
	  echo '--- $(BIN)  (no $(IN); type input, Ctrl-D to end) ---'; \
	  '$(BIN)'; \
	fi

endif

$(BUILDDIR)/%: %.cpp | require-gcc
	@mkdir -p $(dir $@)
	$(GXX) $(CXXFLAGS) -o $@ $<

clean:
	rm -rf build