From 01fcdc8566e26914fc0f38f8ce4c41114dbf6c40 Mon Sep 17 00:00:00 2001 From: Bruno Raoult Date: Fri, 20 Aug 2021 01:02:07 +0200 Subject: [PATCH] C: binary search --- c/binary-search/GNUmakefile | 51 ++++++++++++++++++++ c/binary-search/README.md | 73 +++++++++++++++++++++++++++++ c/binary-search/makefile | 37 +++++++++++++++ c/binary-search/src/binary_search.c | 39 +++++++++++++++ c/binary-search/src/binary_search.h | 20 ++++++++ 5 files changed, 220 insertions(+) create mode 100644 c/binary-search/GNUmakefile create mode 100644 c/binary-search/README.md create mode 100644 c/binary-search/makefile create mode 100644 c/binary-search/src/binary_search.c create mode 100644 c/binary-search/src/binary_search.h diff --git a/c/binary-search/GNUmakefile b/c/binary-search/GNUmakefile new file mode 100644 index 0000000..ec085d0 --- /dev/null +++ b/c/binary-search/GNUmakefile @@ -0,0 +1,51 @@ +# The original 'makefile' has a flaw: +# 1) it overrides CFLAGS +# 2) it does not pass extra "FLAGS" to $(CC) that could come from environment +# +# It means : +# - we need to edit 'makefile' for different builds (DEBUG, etc...), which is +# not practical at all. +# - Also, it does not allow to run all tests without editing the test source +# code. +# +# To use this makefile (GNU make only): +# "make": build with all predefined tests (without editing test source code) +# "make debugall": build with all predefined tests and debug code +# "make mem": perform memcheck with all tests enabled +# "make unit": build standalone (unit) test +# "make debug": build standalone test with debugging code +# +# Original 'makefile' targets can be used (test, memcheck, clean, ...) + +.PHONY: default all mem unit debug std debugtest + +default: all + +# default is to build with all predefined tests +BUILD := teststall + +include makefile + +all: CFLAGS+=-DTESTALL +all: clean test + +debugall: CFLAGS+=-DDEBUG +debugall: all + +debugtest: CFLAGS+=-DDEBUG +debugtest: test + +mem: CFLAGS+=-DTESTALL +mem: clean memcheck + +unit: CFLAGS+=-DUNIT_TEST +unit: clean std + +debug: CFLAGS+=-DUNIT_TEST -DDEBUG +debug: clean std + +debugtest: CFLAGS+=-DDEBUG +debugtest: test + +std: src/*.c src/*.h + $(CC) $(CFLAGS) src/*.c -o test.out diff --git a/c/binary-search/README.md b/c/binary-search/README.md new file mode 100644 index 0000000..4493061 --- /dev/null +++ b/c/binary-search/README.md @@ -0,0 +1,73 @@ +# Binary Search + +Implement a binary search algorithm. + +Searching a sorted collection is a common task. A dictionary is a sorted +list of word definitions. Given a word, one can find its definition. A +telephone book is a sorted list of people's names, addresses, and +telephone numbers. Knowing someone's name allows one to quickly find +their telephone number and address. + +If the list to be searched contains more than a few items (a dozen, say) +a binary search will require far fewer comparisons than a linear search, +but it imposes the requirement that the list be sorted. + +In computer science, a binary search or half-interval search algorithm +finds the position of a specified input value (the search "key") within +an array sorted by key value. + +In each step, the algorithm compares the search key value with the key +value of the middle element of the array. + +If the keys match, then a matching element has been found and its index, +or position, is returned. + +Otherwise, if the search key is less than the middle element's key, then +the algorithm repeats its action on the sub-array to the left of the +middle element or, if the search key is greater, on the sub-array to the +right. + +If the remaining array to be searched is empty, then the key cannot be +found in the array and a special "not found" indication is returned. + +A binary search halves the number of items to check with each iteration, +so locating an item (or determining its absence) takes logarithmic time. +A binary search is a dichotomic divide and conquer search algorithm. + +## Getting Started + +Make sure you have read the "Guides" section of the +[C track][c-track] on the Exercism site. This covers +the basic information on setting up the development environment expected +by the exercises. + +## Passing the Tests + +Get the first test compiling, linking and passing by following the [three +rules of test-driven development][3-tdd-rules]. + +The included makefile can be used to create and run the tests using the `test` +task. + + make test + +Create just the functions you need to satisfy any compiler errors and get the +test to fail. Then write just enough code to get the test to pass. Once you've +done that, move onto the next test. + +As you progress through the tests, take the time to refactor your +implementation for readability and expressiveness and then go on to the next +test. + +Try to use standard C99 facilities in preference to writing your own +low-level algorithms or facilities by hand. + +## Source + +Wikipedia [http://en.wikipedia.org/wiki/Binary_search_algorithm](http://en.wikipedia.org/wiki/Binary_search_algorithm) + +## Submitting Incomplete Solutions +It's possible to submit an incomplete solution so you can see how others have completed the exercise. + +[c-track]: https://exercism.io/my/tracks/c +[3-tdd-rules]: http://butunclebob.com/ArticleS.UncleBob.TheThreeRulesOfTdd diff --git a/c/binary-search/makefile b/c/binary-search/makefile new file mode 100644 index 0000000..f34535a --- /dev/null +++ b/c/binary-search/makefile @@ -0,0 +1,37 @@ +### If you wish to use extra libraries (math.h for instance), +### add their flags here (-lm in our case) in the "LIBS" variable. + +LIBS = -lm + +### +CFLAGS = -std=c99 +CFLAGS += -g +CFLAGS += -Wall +CFLAGS += -Wextra +CFLAGS += -pedantic +CFLAGS += -Werror +CFLAGS += -Wmissing-declarations +CFLAGS += -DUNITY_SUPPORT_64 + +ASANFLAGS = -fsanitize=address +ASANFLAGS += -fno-common +ASANFLAGS += -fno-omit-frame-pointer + +.PHONY: test +test: tests.out + @./tests.out + +.PHONY: memcheck +memcheck: test/*.c src/*.c src/*.h + @echo Compiling $@ + @$(CC) $(ASANFLAGS) $(CFLAGS) src/*.c test/vendor/unity.c test/*.c -o memcheck.out $(LIBS) + @./memcheck.out + @echo "Memory check passed" + +.PHONY: clean +clean: + rm -rf *.o *.out *.out.dSYM + +tests.out: test/*.c src/*.c src/*.h + @echo Compiling $@ + @$(CC) $(CFLAGS) src/*.c test/vendor/unity.c test/*.c -o tests.out $(LIBS) diff --git a/c/binary-search/src/binary_search.c b/c/binary-search/src/binary_search.c new file mode 100644 index 0000000..b75ac9c --- /dev/null +++ b/c/binary-search/src/binary_search.c @@ -0,0 +1,39 @@ +#include "binary_search.h" + +const int *binary_search(int v, const int *a, size_t size) +{ + size_t lo, hi, i; + + /* quickly exclude invalid/trivial results : + * NULL or empty array, value out of bounds + */ + if (!size || !a || v < *a || v > *(a+size-1)) + return NULL; + for (lo=0, hi=size-1, i=hi/2; lo +int main(int ac, char **av) +{ + int arg=1, *res; + int i, array[] = {1, 2, 3, 4, 6, 7, 8, 9 }; + size_t size = sizeof(array) / sizeof(array[0]); + + for (; arg + +const int *binary_search(int value, const int *arr, size_t length); + +/* See GNUmakefile below for explanation + * https://github.com/braoult/exercism/blob/master/c/templates/GNUmakefile + */ +#if defined UNIT_TEST || defined DEBUG +#include +#include +#endif +#ifdef TESTALL +#undef TEST_IGNORE +#define TEST_IGNORE() {} +#endif + +#endif