commit b84420fdf1df78a4cc7369e182b09d3123811dbc
Author: dimakuv <dmitry.kuvayskiy@gmail.com>
Date:   Sat Apr 25 15:31:21 2015 +0200

    initial commit

diff --git a/c_sequential/3sat/3sat.c b/c_sequential/3sat/3sat.c
new file mode 100644
index 0000000..2829ff4
--- /dev/null
+++ b/c_sequential/3sat/3sat.c
@@ -0,0 +1,97 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+// Solves the 3-SAT system using an exaustive search
+// It finds all the possible values for the set of variables using
+// a number. The binary representation of this number represents 
+// the values of the variables. Since a long variable has 64 bits, 
+// this implementations works with problems with up to 64 variables.
+long solveClauses(short **clauses, int nClauses, int nVar) {
+
+	long *iVar = (long *) malloc(nVar * sizeof(long));
+	int i;
+	for (i = 0; i < nVar; i++)
+		iVar[i] = exp2(i);
+
+	unsigned long maxNumber = exp2(nVar);
+	long number;
+	short var;
+	int c;
+
+	for (number = 0; number < maxNumber; number++) {
+
+		for (c = 0; c < nClauses; c++) {
+
+			var = clauses[0][c];
+			if (var > 0 && (number & iVar[var - 1]) > 0)
+				continue; // clause is true
+			else if (var < 0 && (number & iVar[-var - 1]) == 0)
+				continue; // clause is true
+
+			var = clauses[1][c];
+			if (var > 0 && (number & iVar[var - 1]) > 0)
+				continue; // clause is true
+			else if (var < 0 && (number & iVar[-var - 1]) == 0)
+				continue; // clause is true
+
+			var = clauses[2][c];
+			if (var > 0 && (number & iVar[var - 1]) > 0)
+				continue; // clause is true
+			else if (var < 0 && (number & iVar[-var - 1]) == 0)
+				continue; // clause is true
+
+			break; // clause is false
+		}
+
+		if (c == nClauses)
+			return number;
+
+	}
+	return -1;
+
+}
+
+// Read nClauses clauses of size 3. nVar represents the number of variables
+// Clause[0][i], Clause[1][i] and Clause[2][i] contains the 3 elements of the i-esime clause.
+// Each element of the caluse vector may contain values selected from:
+// k = -nVar, ..., -2, -1, 1, 2, ..., nVar. The value of k represents the index of the variable.
+// A negative value remains the negation of the variable.
+short **readClauses(int nClauses, int nVar) {
+
+	short **clauses = (short **) malloc(3 * sizeof(short *));
+	clauses[0] = (short *) malloc(nClauses * sizeof(short));
+	clauses[1] = (short *) malloc(nClauses * sizeof(short));
+	clauses[2] = (short *) malloc(nClauses * sizeof(short));
+
+	int i;
+	for (i = 0; i < nClauses; i++) {
+		scanf("%hd %hd %hd", &clauses[0][i], &clauses[1][i], &clauses[2][i]);
+	}
+
+	return clauses;
+}
+
+int main(int argc, char *argv[]) {
+
+	int nClauses;
+	int nVar;
+
+	scanf("%d %d", &nClauses, &nVar);
+
+	short **clauses = readClauses(nClauses, nVar);
+
+	long solution = solveClauses(clauses, nClauses, nVar);
+
+	int i;
+	if (solution >= 0) {
+		printf("Solution found [%ld]: ", solution);
+		for (i = 0; i < nVar; i++)
+			printf("%d ", (int) ((solution & (long) exp2(i)) / exp2(i)));
+		printf("\n");
+	} else
+		printf("Solution not found.\n");
+
+	return EXIT_SUCCESS;
+}
+
diff --git a/c_sequential/3sat/Makefile b/c_sequential/3sat/Makefile
new file mode 100644
index 0000000..4b34c9c
--- /dev/null
+++ b/c_sequential/3sat/Makefile
@@ -0,0 +1,19 @@
+CC    = gcc
+FLAGS = -O3 -Wall -Wno-unused-result
+
+SRC   = 3sat.c
+EXEC  = bin/3sat
+
+all: make_dirs $(EXEC)
+
+clean:
+	rm -f -r bin
+
+make_dirs:
+	mkdir -p bin
+
+$(EXEC): $(SRC)
+	$(CC) $(FLAGS) $^ -o $@ -lm
+
+run:
+	./$(EXEC) < input/small1.in
diff --git a/c_sequential/bucketsort/Makefile b/c_sequential/bucketsort/Makefile
new file mode 100644
index 0000000..a886663
--- /dev/null
+++ b/c_sequential/bucketsort/Makefile
@@ -0,0 +1,20 @@
+CC    = gcc
+FLAGS = -O3 -Wall -Wno-unused-result
+
+SRC   = bucketsort.c main.c
+EXEC  = bin/bucketsort
+
+all: make_dirs $(EXEC)
+
+clean:
+	rm -f -r bin
+
+make_dirs:
+	mkdir -p bin
+
+$(EXEC): $(SRC)
+	$(CC) $(FLAGS) $^ -o $@
+
+run:
+	./$(EXEC) input/medium.in input/medium.out
+
diff --git a/c_sequential/bucketsort/bucketsort.c b/c_sequential/bucketsort/bucketsort.c
new file mode 100644
index 0000000..888ffb2
--- /dev/null
+++ b/c_sequential/bucketsort/bucketsort.c
@@ -0,0 +1,54 @@
+#include <stdlib.h>
+#include <string.h>
+#include "bucketsort.h"
+
+#define N_BUCKETS 94
+
+typedef struct {
+	long int *data;
+	int length;
+	long int total;
+} bucket;
+
+void sort(char *a, bucket *bucket) {
+	int j, i, length;
+	long int key;
+	length = bucket->length;
+	for (j = 1; j < bucket->total; j++) {
+		key = bucket->data[j];
+		i = j - 1;
+		while (i >= 0
+				&& strcmp(a + bucket->data[i] * length, a + key * length) > 0) {
+			bucket->data[i + 1] = bucket->data[i];
+			i--;
+		}
+		bucket->data[i + 1] = key;
+	}
+}
+
+long int* bucket_sort(char *a, int length, long int size) {
+
+	long int i;
+	bucket buckets[N_BUCKETS], *b;
+	long int *returns;
+
+	// allocate memory
+	returns = malloc(sizeof(long int) * size);
+	for (i = 0; i < N_BUCKETS; i++) {
+		buckets[i].data = returns + i * size / N_BUCKETS;
+		buckets[i].length = length;
+		buckets[i].total = 0;
+	}
+
+	// copy the keys to "buckets"
+	for (i = 0; i < size; i++) {
+		b = &buckets[*(a + i * length) - 0x21];
+		b->data[b->total++] = i;
+	}
+
+	// sort each "bucket"
+	for (i = 0; i < N_BUCKETS; i++)
+		sort(a, &buckets[i]);
+
+	return returns;
+}
diff --git a/c_sequential/bucketsort/bucketsort.h b/c_sequential/bucketsort/bucketsort.h
new file mode 100644
index 0000000..ad891cf
--- /dev/null
+++ b/c_sequential/bucketsort/bucketsort.h
@@ -0,0 +1,6 @@
+#ifndef BUCKETSORT_H_
+#define BUCKETSORT_H_
+
+long int* bucket_sort(char *, int, long int);
+
+#endif /* BUCKETSORT_H_ */
diff --git a/c_sequential/bucketsort/main.c b/c_sequential/bucketsort/main.c
new file mode 100644
index 0000000..8a4bc6d
--- /dev/null
+++ b/c_sequential/bucketsort/main.c
@@ -0,0 +1,65 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "bucketsort.h"
+
+#define LENGTH 8
+
+FILE *fin, *fout;
+
+char *strings;
+long int N;
+
+void openfiles(char* in, char* out) {
+	fin = fopen(in, "r+");
+	if (fin == NULL) {
+		perror("fopen fin");
+		exit(EXIT_FAILURE);
+	}
+
+	fout = fopen(out, "w");
+	if (fout == NULL) {
+		perror("fopen fout");
+		exit(EXIT_FAILURE);
+	}
+}
+
+void closefiles(void) {
+	fclose(fin);
+	fclose(fout);
+}
+
+int main(int argc, char* argv[]) {
+	long int i, *r;
+
+    if (argc != 3) {
+        printf("usage: %s [input_file] [output_file]\n", argv[0]);
+        return 0;
+    }
+
+	openfiles(argv[1], argv[2]);
+
+	fscanf(fin, "%ld", &N);
+	strings = (char*) malloc(N * LENGTH);
+	if (strings == NULL) {
+		perror("malloc strings");
+		exit(EXIT_FAILURE);
+	}
+
+	for (i = 0; i < N; i++)
+		fscanf(fin, "%s", strings + (i * LENGTH));
+
+	fflush(stdout);
+
+	r = bucket_sort(strings, LENGTH, N);
+
+	fflush(stdout);
+
+	for (i = 0; i < N; i++)
+		fprintf(fout, "%s\n", strings + (r[i] * LENGTH));
+
+	free(r);
+	free(strings);
+	closefiles();
+
+	return EXIT_SUCCESS;
+}
diff --git a/c_sequential/friendly/Makefile b/c_sequential/friendly/Makefile
new file mode 100644
index 0000000..20d727a
--- /dev/null
+++ b/c_sequential/friendly/Makefile
@@ -0,0 +1,20 @@
+CC    = gcc
+FLAGS = -O3 -Wall -Wno-unused-result
+
+SRC   = friendly.c
+EXEC  = bin/friendly
+
+all: make_dirs $(EXEC)
+
+clean:
+	rm -f -r bin
+
+make_dirs:
+	mkdir -p bin
+
+$(EXEC): $(SRC)
+	$(CC) $(FLAGS) $^ -o $@
+
+run:
+	./$(EXEC) < input/small.in
+
diff --git a/c_sequential/friendly/friendly.c b/c_sequential/friendly/friendly.c
new file mode 100644
index 0000000..2f572c7
--- /dev/null
+++ b/c_sequential/friendly/friendly.c
@@ -0,0 +1,69 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+int gcd(int u, int v) {
+	if (v == 0)
+		return u;
+	return gcd(v, u % v);
+}
+
+void friendly_numbers(long int start, long int end) {
+	long int last = end - start + 1;
+
+	long int *the_num;
+	the_num = (long int*) malloc(sizeof(long int) * last);
+	long int *num;
+	num = (long int*) malloc(sizeof(long int) * last);
+	long int *den;
+	den = (long int*) malloc(sizeof(long int) * last);
+
+	long int i, j, factor, ii, sum, done, n;
+
+	for (i = start; i <= end; i++) {
+		ii = i - start;
+		sum = 1 + i;
+		the_num[ii] = i;
+		done = i;
+		factor = 2;
+		while (factor < done) {
+			if ((i % factor) == 0) {
+				sum += (factor + (i / factor));
+				if ((done = i / factor) == factor)
+					sum -= factor;
+			}
+			factor++;
+		}
+		num[ii] = sum;
+		den[ii] = i;
+		n = gcd(num[ii], den[ii]);
+		num[ii] /= n;
+		den[ii] /= n;
+	} // end for
+
+	for (i = 0; i < last; i++) {
+		for (j = i + 1; j < last; j++) {
+			if ((num[i] == num[j]) && (den[i] == den[j]))
+				printf("%ld and %ld are FRIENDLY\n", the_num[i], the_num[j]);
+		}
+	}
+
+	free(the_num);
+	free(num);
+	free(den);
+}
+
+int main(int argc, char **argv) {
+	long int start;
+	long int end;
+
+	while (1) {
+		scanf("%ld %ld", &start, &end);
+		if (start == 0 && end == 0)
+			break;
+		printf("Number %ld to %ld\n", start, end);
+		friendly_numbers(start, end);
+	}
+
+	return EXIT_SUCCESS;
+}
diff --git a/c_sequential/haar/Makefile b/c_sequential/haar/Makefile
new file mode 100644
index 0000000..2b19c6b
--- /dev/null
+++ b/c_sequential/haar/Makefile
@@ -0,0 +1,27 @@
+CC    = gcc
+FLAGS = -O3 -Wall -Wno-unused-result
+
+SRC   = haar.c
+EXEC  = bin/haar
+GEN   = bin/input_generator
+
+all: make_dirs $(EXEC) $(GEN)
+
+clean:
+	rm -f -r bin
+	rm -f -r input
+
+make_dirs:
+	mkdir -p bin
+	mkdir -p input
+
+$(EXEC): $(SRC)
+	$(CC) $(FLAGS) $^ -o $@
+
+$(GEN): input_generator.c
+	$(CC) $(FLAGS) $^ -o $@
+
+run:
+	./$(GEN) input/medium.in
+	./$(EXEC) input/medium.in input/medium.out
+
diff --git a/c_sequential/haar/haar.c b/c_sequential/haar/haar.c
new file mode 100644
index 0000000..1fa9989
--- /dev/null
+++ b/c_sequential/haar/haar.c
@@ -0,0 +1,127 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+#include <time.h>
+#include <stdint.h>
+
+#define pixel(x,y) pixels[((y)*size)+(x)]
+
+//#define DEBUG
+
+void print(int *pixels, int size) {
+	int x, y;
+	for (y = 0; y < size; y++) {
+		for (x = 0; x < size; x++) {
+			printf("%10d ", pixel(x,y));
+		}
+		printf("\n");
+		fflush(stdout);
+	}
+}
+
+int main(int argc, char *argv[]) {
+    if (argc != 3) {
+        printf("usage: %s [input_file] [output_file]\n", argv[0]);
+        return 0;
+    }
+
+	FILE *in;
+	FILE *out;
+
+    clock_t start;
+    clock_t end;
+
+	in = fopen(argv[1], "rb");
+	if (in == NULL) {
+		perror(argv[1]);
+		exit(EXIT_FAILURE);
+	}
+
+	out = fopen(argv[2], "wb");
+	if (out == NULL) {
+		perror(argv[2]);
+		exit(EXIT_FAILURE);
+	}
+
+	long long int s, size, mid;
+	int x, y;
+	long long int a, d;
+	double SQRT_2;
+
+	fread(&size, sizeof(size), 1, in);
+
+	fwrite(&size, sizeof(size), 1, out);
+
+	int *pixels = (int *) malloc(size * size * sizeof(int));
+
+    start = clock();
+	if (!fread(pixels, size * size * sizeof(int), 1, in)) {
+		perror("read error");
+		exit(EXIT_FAILURE);
+	}
+    end = clock();
+    printf("time to read: %ju (%f s)\n", (uintmax_t)(end - start), (float)(end - start) / CLOCKS_PER_SEC);
+
+#ifdef DEBUG
+	printf("origin: %lld\n", size);
+	print(pixels, size);
+#endif
+
+	// haar
+    start = clock();
+
+	SQRT_2 = sqrt(2);
+	for (s = size; s > 1; s /= 2) {
+		mid = s / 2;
+		// row-transformation
+		for (y = 0; y < mid; y++) {
+			for (x = 0; x < mid; x++) {
+				a = pixel(x,y);
+				a = (a+pixel(mid+x,y))/SQRT_2;
+				d = pixel(x,y);
+				d = (d-pixel(mid+x,y))/SQRT_2;
+				pixel(x,y) = a;
+				pixel(mid+x,y) = d;
+			}
+		}
+
+#ifdef DEBUG
+		printf("after row-transformation: %lld\n", mid);
+		print(pixels, size);
+#endif
+		// column-transformation
+		for (y = 0; y < mid; y++) {
+			for (x = 0; x < mid; x++) {
+				a = pixel(x,y);
+				a = (a+pixel(x,mid+y))/SQRT_2;
+				d = pixel(x,y);
+				d = (d-pixel(x,mid+y))/SQRT_2;
+				pixel(x,y) = a;
+				pixel(x,mid+y) = d;
+			}
+		}
+
+#ifdef DEBUG
+		printf("after column-transformation: %lld\n", mid);
+		print(pixels, size);
+#endif
+	}
+
+    end = clock();
+    printf("time to haar: %ju (%f s)\n", (uintmax_t)(end - start), (float)(end - start) / CLOCKS_PER_SEC);
+
+    start = clock();
+
+	fwrite(pixels, size * size * sizeof(int), 1, out);
+
+    end = clock();
+    printf("time to write: %ju (%f s)\n", (uintmax_t)(end - start), (float)(end - start) / CLOCKS_PER_SEC);
+
+	free(pixels);
+
+	fclose(out);
+	fclose(in);
+
+	return EXIT_SUCCESS;
+}
diff --git a/c_sequential/haar/input_generator.c b/c_sequential/haar/input_generator.c
new file mode 100644
index 0000000..29bc1c8
--- /dev/null
+++ b/c_sequential/haar/input_generator.c
@@ -0,0 +1,54 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <math.h>
+
+// change size to make image bigger/smaller
+#define IMGSIZE 0x3000  // 0x6000
+
+#define image(x,y) pixels[((unsigned int)y*size+x)]
+
+// generates an image
+int main(int argc, char *argv[]) {
+    if (argc != 2) {
+        printf("usage: %s [create_file]", argv[0]);
+        return 0;
+    }
+
+	unsigned long long int size;
+	unsigned long long int x, y;
+
+	FILE *out;
+	srand(time(NULL));
+
+	out = fopen(argv[1], "wb");
+	if (out == NULL ) {
+		perror(argv[1]);
+		exit(EXIT_FAILURE);
+	}
+
+	size = IMGSIZE;
+	printf("%lld\n", size);
+
+	fwrite(&size, sizeof(size), 1, out);
+	fflush(out);
+
+	int *pixels = (int*) malloc(size * size * sizeof(int));
+	if (pixels == NULL ) {
+		perror("malloc pixels");
+		exit(EXIT_FAILURE);
+	}
+
+	for (y = 0; y < size; y++) {
+		for (x = 0; x < size; x++) {
+			image(x,y)= (rand()&0xFFFF);
+		}
+	}
+	fwrite(pixels, size * size * sizeof(int), 1, out);
+
+	fflush(out);
+	fclose(out);
+	free(pixels);
+
+	return EXIT_SUCCESS;
+}
diff --git a/c_sequential/knapsack/Makefile b/c_sequential/knapsack/Makefile
new file mode 100644
index 0000000..bf7111e
--- /dev/null
+++ b/c_sequential/knapsack/Makefile
@@ -0,0 +1,20 @@
+CC    = gcc
+FLAGS = -O3 -Wall -Wno-unused-result
+
+SRC   = knapsack.c
+EXEC  = bin/knapsack
+
+all: make_dirs $(EXEC)
+
+clean:
+	rm -f -r bin
+
+make_dirs:
+	mkdir -p bin
+
+$(EXEC): $(SRC)
+	$(CC) $(FLAGS) $^ -o $@
+
+run:
+	./$(EXEC) < input/small.in
+
diff --git a/c_sequential/knapsack/knapsack.c b/c_sequential/knapsack/knapsack.c
new file mode 100644
index 0000000..306e926
--- /dev/null
+++ b/c_sequential/knapsack/knapsack.c
@@ -0,0 +1,67 @@
+/* @author St\'efano Drimon Kurz M\'or */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+typedef struct _item_t {
+	int value;   // v_i
+	int weight;  // w_i
+	float density; // v_i/w_i
+} item_t;
+
+int greater_f(const int x, const int y);
+int compare_f(const void *x, const void *y);
+
+int knapsack_f(const int n, const int M, const item_t * const itens) {
+
+	int v = 0, w = 0;
+	int r = 0;
+
+	if (n < 1)
+		return 0;
+
+	while (M - w >= 0) {
+		r = greater_f(r, v + knapsack_f(n - 1, M - w, &(itens[1])));
+		v += itens[0].value;
+		w += itens[0].weight;
+	}
+
+	return r;
+
+}
+
+int main(int argc, const char *argv[]) {
+
+	int n;
+	int M;
+	item_t *itens;
+
+	int i;
+
+	scanf("%d %d", &n, &M);
+	itens = (item_t*) calloc(n, sizeof(item_t));
+
+	for (i = 0; i < n; ++i) {
+		scanf("%d %d", &(itens[i].value), &(itens[i].weight));
+		itens[i].density = (float) (itens[i].value) / itens[i].weight;
+	}
+
+	qsort(itens, (size_t) n, sizeof(item_t), compare_f);
+
+	printf("%d\n", knapsack_f(n, M, itens));
+
+	free(itens);
+
+	return 0;
+
+}
+
+int greater_f(const int x, const int y) {
+	return (x > y) ? x : y;
+}
+
+int compare_f(const void *x, const void *y) {
+	return ((item_t*) x)->density - ((item_t*) y)->density;
+}
+
diff --git a/problemset.pdf b/problemset.pdf
new file mode 100644
index 0000000..e78cc58
Binary files /dev/null and b/problemset.pdf differ