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#include <stdlib.h>
#include <stdio.h>
#define N 20
int nb_num;
int tab[N];
int stack_ptr;
int stack_op[N];
int stack_res[60];
int result;
int find(int n, int i1, int a, int b, int op)
{
int i, j;
int c;
if (stack_ptr >= 0) {
stack_res[3*stack_ptr] = a;
stack_op[stack_ptr] = op;
stack_res[3*stack_ptr+1] = b;
stack_res[3*stack_ptr+2] = n;
if (n == result)
return 1;
tab[i1] = n;
}
for(i=0;i<nb_num;i++) {
for(j=i+1;j<nb_num;j++) {
a = tab[i];
b = tab[j];
if (a != 0 && b != 0) {
tab[j] = 0;
stack_ptr++;
if (find(a + b, i, a, b, '+'))
return 1;
if (find(a - b, i, a, b, '-'))
return 1;
if (find(b - a, i, b, a, '-'))
return 1;
if (find(a * b, i, a, b, '*'))
return 1;
if (b != 0) {
c = a / b;
if (find(c, i, a, b, '/'))
return 1;
}
if (a != 0) {
c = b / a;
if (find(c, i, b, a, '/'))
return 1;
}
stack_ptr--;
tab[i] = a;
tab[j] = b;
}
}
}
return 0;
}
int main(int argc, char **argv)
{
int i, res, p;
if (argc < 3) {
printf("usage: %s: result numbers...\n"
"Try to find result from numbers with the 4 basic operations.\n", argv[0]);
exit(1);
}
p = 1;
result = atoi(argv[p]);
printf("result=%d\n", result);
nb_num = 0;
for(i=p+1;i<argc;i++) {
tab[nb_num++] = atoi(argv[i]);
}
stack_ptr = -1;
res = find(0, 0, 0, 0, ' ');
if (res) {
for(i=0;i<=stack_ptr;i++) {
printf("%d %c %d = %d\n",
stack_res[3*i], stack_op[i],
stack_res[3*i+1], stack_res[3*i+2]);
}
return 0;
} else {
printf("Impossible\n");
return 1;
}
}
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