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#include <stdio.h>
#include <string.h>
#include <malloc.h>
#include <limits.h>
#include <stdint.h>
#include "solver.h"
#define _log(...) fprintf(stderr, __VA_ARGS__)
#define _abs(x) (((x) < 0) ? -(x) : (x))
typedef uint8_t byte;
enum {
addition,
substraction,
multiplication,
division,
};
typedef struct {
int v1;
int v2;
byte op;
} computation_t;
typedef struct {
computation_t *computation;
int level;
} solution_t;
static solution_t solution_g;
static int result;
static int closer = -1;
/* {{{ display */
static void display_solution(void)
{
puts("--------------------------");
puts("found a (better) solution:");
for (int i = 5; i >= solution_g.level; i--) {
char op;
int _result;
switch (solution_g.computation[i].op) {
case addition:
op = '+';
_result = solution_g.computation[i].v1 + solution_g.computation[i].v2;
break;
case substraction:
op = '-';
_result = solution_g.computation[i].v1 - solution_g.computation[i].v2;
break;
case multiplication:
op = '*';
_result = solution_g.computation[i].v1 * solution_g.computation[i].v2;
break;
case division:
op = '/';
_result = solution_g.computation[i].v1 / solution_g.computation[i].v2;
break;
}
printf("%d %c %d = %d\n", solution_g.computation[i].v1
, op
, solution_g.computation[i].v2
, _result);
}
}
/* }}} */
static inline
void construct_new_vect(vect_t *new_vect, vect_t *vect, unsigned v1, unsigned v2)
{
unsigned j = 0;
for (unsigned i = 0; i < vect->len; ++i) {
/* check is this is one of the taken values */
if (i == v1 || i == v2)
continue;
new_vect->array[j++] = vect->array[i];
}
}
static void solve_rec(vect_t *vect)
{
vect_t new_vect;
if (solution_g.level != 0 && ((unsigned)solution_g.level >= vect->len)) {
/* we have already found a better solution */
return;
}
if (vect->len == 0)
return;
for (unsigned i = 0; i < vect->len; ++i) {
if ((closer == -1)
|| (_abs(vect->array[i] - result) <= _abs(closer - result)))
{
closer = vect->array[i];
if (closer == result) {
solution_g.level = vect->len;
display_solution();
return;
}
}
}
new_vect.array = malloc(sizeof(int) * (vect->len - 1));
new_vect.len = vect->len - 1;
for (unsigned i = 0; i < vect->len; ++i) {
for (unsigned j = 0; j < vect->len; ++j) {
/* we cannot use the same value twice */
if (i == j)
continue;
/* construct the new vector */
construct_new_vect(&new_vect, vect, i, j);
solution_g.computation[vect->len - 1].v1 = vect->array[i];
solution_g.computation[vect->len - 1].v2 = vect->array[j];
/* try adding (no condition) */
new_vect.array[new_vect.len - 1] = vect->array[i] + vect->array[j];
solution_g.computation[vect->len - 1].op = addition;
solve_rec(&new_vect);
/* try substracting (must be > 0) */
if (vect->array[i] >= vect->array[j]) {
new_vect.array[new_vect.len - 1] = vect->array[i] - vect->array[j];
solution_g.computation[vect->len - 1].op = substraction;
solve_rec(&new_vect);
}
/* try multiplicating (no condition) */
new_vect.array[new_vect.len - 1] = vect->array[i] * vect->array[j];
solution_g.computation[vect->len - 1].op = multiplication;
solve_rec(&new_vect);
/* try dividing (no rest needed and cannot divide by 0) */
if ((vect->array[j] != 0) && (vect->array[i] % vect->array[j] == 0)) {
new_vect.array[new_vect.len - 1] = vect->array[i] / vect->array[j];
solution_g.computation[vect->len - 1].op = division;
solve_rec(&new_vect);
}
}
}
free(new_vect.array);
}
/* public function to use */
void solve(vect_t *vect, int _result)
{
result = _result;
solution_g.computation = malloc(sizeof(computation_t) * vect->len);
solution_g.level = 0;
solve_rec(vect);
if (closer != result) {
result = closer;
closer = -1;
solve_rec(vect);
}
free(solution_g.computation);
}
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