nissy-classic

utils.c (3585B)

---

 #include "utils.h"
 
 void
 apply_permutation(int *perm, int *set, int n)
 {
 	int i;
 	int aux[n];
 
 	if (!is_perm(perm, n))
 		return;
 		
 	for (i = 0; i < n; i++)
 		aux[i] = set[perm[i]];
 
 	memcpy(set, aux, n * sizeof(int));
 }
 
 int
 binomial(int n, int k)
 {
 	if (n < 0 || k < 0 || k > n)
 		return 0;
 
 	return factorial(n) / (factorial(k) * factorial(n-k));
 }
 
 int
 digit_array_to_int(int *a, int n, int b)
 {
 	int i, ret = 0, p = 1;
 
 	for (i = 0; i < n; i++, p *= b)
 		ret += a[i] * p;
 
 	return ret;
 }
 
 int
 factorial(int n)
 {
 	int i, ret = 1;
 
 	if (n < 0)
 		return 0;
 
 	for (i = 1; i <= n; i++)
 		ret *= i;
 
 	return ret;
 }
 
 void
 index_to_perm(int p, int n, int *r)
 {
 	int i, j, c;
 	int a[n];
 
 	for (i = 0; i < n; i++)
 		a[i] = 0;
 
 	if (p < 0 || p >= factorial(n))
 		for (i = 0; i < n; i++)
 			r[i] = -1;
 
 	for (i = 0; i < n; i++) {
 		c = 0;
 		j = 0;
 		while (c <= p / factorial(n-i-1))
 			c += a[j++] ? 0 : 1;
 		r[i] = j-1;
 		a[j-1] = 1;
 		p %= factorial(n-i-1);
 	}
 }
 
 void
 index_to_subset(int s, int n, int k, int *r)
 {
 	int i, j, v;
 
 	if (s < 0 || s >= binomial(n, k)) {
 		for (i = 0; i < n; i++)
 			r[i] = -1;
 		return;
 	}
 
 	for (i = 0; i < n; i++) {
 		if (k == n-i) {
 			for (j = i; j < n; j++)
 				r[j] = 1;
 			return;
 		}
 
 		if (k == 0) {
 			for (j = i; j < n; j++)
 				r[j] = 0;
 			return;
 		}
 
 		v = binomial(n-i-1, k);
 		if (s >= v) {
 			r[i] = 1;
 			k--;
 			s -= v;
 		} else {
 			r[i] = 0;
 		}
 	}
 }
 
 void
 int_to_digit_array(int a, int b, int n, int *r)
 {
 	int i;
 
 	if (b <= 1)
 		for (i = 0; i < n; i++)
 			r[i] = 0;
 	else
 		for (i = 0; i < n; i++, a /= b)
 			r[i] = a % b;
 }
 
 void
 int_to_sum_zero_array(int x, int b, int n, int *a)
 {
 	int i, s = 0;
 
 	if (b <= 1) {
 		for (i = 0; i < n; i++)
 		    a[i] = 0;
 	} else {
 		int_to_digit_array(x, b, n-1, a);
 		for (i = 0; i < n - 1; i++)
 		    s = (s + a[i]) % b;
 		a[n-1] = (b - s) % b;
 	}
 }
 
 int
 invert_digits(int a, int b, int n)
 {
 	int i, ret;
 	int r[n];
 
 	int_to_digit_array(a, b, n, r);
 	for (i = 0; i < n; i++)
 		r[i] = (b-r[i]) % b;
 
 	ret = digit_array_to_int(r, n, b);
 	return ret;
 }
 
 bool
 is_perm(int *a, int n)
 {
 	int i;
 	int aux[n];
 
 	for (i = 0; i < n; i++)
 		aux[i] = 0;
 	
 	for (i = 0; i < n; i++) {
 		if (a[i] < 0 || a[i] >= n)
 			return false;
 		else
 			aux[a[i]] = 1;
 	}
 
 	for (i = 0; i < n; i++)
 		if (!aux[i])
 			return false;
 
 	return true;
 }
 
 bool
 is_subset(int *a, int n, int k)
 {
 	int i, sum = 0;
 
 	for (i = 0; i < n; i++)
 		sum += a[i] ? 1 : 0;
 
 	return sum == k;
 }
 
 int
 perm_sign(int *a, int n)
 {
 	int i, j, ret = 0;
 
 	if (!is_perm(a,n))
 		return -1;
 
 	for (i = 0; i < n; i++)
 		for (j = i+1; j < n; j++)
 			ret += (a[i] > a[j]) ? 1 : 0;
 
 	return ret % 2;
 }
 
 int
 perm_to_index(int *a, int n)
 {
 	int i, j, c, ret = 0;
 
 	if (!is_perm(a, n))
 		return -1;
 
 	for (i = 0; i < n; i++) {
 		c = 0;
 		for (j = i+1; j < n; j++)
 			c += (a[i] > a[j]) ? 1 : 0;
 		ret += factorial(n-i-1) * c;
 	}
 
 	return ret;
 }
 
 int
 powint(int a, int b)
 {
 	if (b < 0)
 		return 0;
 	if (b == 0)
 		return 1;
 
 	if (b % 2)
 		return a * powint(a, b-1);
 	else
 		return powint(a*a, b/2);
 }
 
 int 
 subset_to_index(int *a, int n, int k)
 {
 	int i, ret = 0;
 
 	if (!is_subset(a, n, k))
 		return binomial(n, k);
 
 	for (i = 0; i < n; i++) {
 		if (k == n-i)
 			return ret;
 		if (a[i]) {
 			ret += binomial(n-i-1, k);
 			k--;
 		}
 	}
 
 	return ret;
 }
 
 void
 sum_arrays_mod(int *src, int *dst, int n, int m)
 {
 	int i;
 
 	for (i = 0; i < n; i++)
 		dst[i] = (m <= 0) ? 0 : (src[i] + dst[i]) % m;
 }
 
 void
 swap(int *a, int *b)
 {
 	int aux;
 
 	aux = *a;
 	*a  = *b;
 	*b  = aux;
 }
 
 void
 swapu64(uint64_t *a, uint64_t *b)
 {
 	uint64_t aux;
 
 	aux = *a;
 	*a  = *b;
 	*b  = aux;
 }