Submission #71020354

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#include <stdio.h>
#define MOD_BY 1000000007
int add(int a, int b) {
  return a + b - MOD_BY * (a + b >= MOD_BY);
}
int N;
int a[24][24];
int memo[1 << 24];
int calc(int pos, int used) {
  int ans = 0;
  int i;
  if (pos >= N) return 1;
  if (memo[used]) return ~memo[used];
  for (i = 0; i < N; i++) {
    if (a[pos][i] && !((used >> i) & 1)) {
      ans = add(ans, calc(pos + 1, used | (1 << i)));
 
 
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#include <stdio.h>

#define MOD_BY 1000000007

int add(int a, int b) {
	return a + b - MOD_BY * (a + b >= MOD_BY);
}

int N;
int a[24][24];

int memo[1 << 24];

int calc(int pos, int used) {
	int ans = 0;
	int i;
	if (pos >= N) return 1;
	if (memo[used]) return ~memo[used];
	for (i = 0; i < N; i++) {
		if (a[pos][i] && !((used >> i) & 1)) {
			ans = add(ans, calc(pos + 1, used | (1 << i)));
		}
	}
	return ~(memo[used] = ~ans);
}

int main(void) {
	int i, j;
	if (scanf("%d", &N) != 1) return 1;
	for (i = 0; i < N; i++) {
		for (j = 0; j < N; j++) {
			if (scanf("%d", &a[i][j]) != 1) return 1;
		}
	}
	printf("%d\n", calc(0, 0));
	return 0;
}

Submission Info

Judge Result