Submission #67415085

Source Code Expand

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#include <stdio.h>
/* {1,2,3} -> ... -> {3,2,1} */
int next_permutation(int arr[], int n) {
  int target;
  int i;
  int temp;
  for (i = n - 2; i >= 0; i--) {
    if (arr[i] < arr[i + 1]) break;
  }
  if (i < 0) return 0;
  target = i;
  for (i = 0; target + i + 1 < n - i - 1; i++) {
    temp = arr[target + 1 + i];
    arr[target + 1 + i] = arr[n - 1 - i];
    arr[n - i - 1] = temp;
  }
  for (i = target + 1; i < n; i++) {
    if (arr[i] > arr[target]) break;
 
 
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#include <stdio.h>

/* {1,2,3} -> ... -> {3,2,1} */
int next_permutation(int arr[], int n) {
	int target;
	int i;
	int temp;
	for (i = n - 2; i >= 0; i--) {
		if (arr[i] < arr[i + 1]) break;
	}
	if (i < 0) return 0;
	target = i;

	for (i = 0; target + i + 1 < n - i - 1; i++) {
		temp = arr[target + 1 + i];
		arr[target + 1 + i] = arr[n - 1 - i];
		arr[n - i - 1] = temp;
	}

	for (i = target + 1; i < n; i++) {
		if (arr[i] > arr[target]) break;
	}
	temp = arr[i];
	arr[i] = arr[target];
	arr[target] = temp;
	return 1;
}

int N, M;
char edges[10][10];

int main(void) {
	int i, j, g;
	int ans = 9999;
	if (scanf("%d%d", &N, &M) != 2) return 1;
	for (i = 0; i < M; i++) {
		int A, B;
		if (scanf("%d%d", &A, &B) != 2) return 1;
		if (A < B) edges[A][B] = 1; else edges[B][A] = 1;
	}
	for (g = 0; g < (1 << (N - 1)); g++) {
		int groupA[10], groupB[10], acnt = 0, bcnt = 0;
		for (i = 0; i < N; i++) {
			if ((g >> i) & 1) groupB[bcnt++] = i + 1; else groupA[acnt++] = i + 1;
		}
		if (acnt < 3 || (bcnt < 3 && bcnt != 0)) continue;
		do {
			int groupBp[10];
			for (i = 0; i < bcnt; i++) groupBp[i] = groupB[i];
			do {
				char edges_target[10][10] = {{0}};
				int score = 0;
				for (i = 0; i < acnt; i++) {
					int x = groupA[i], y = groupA[(i + 1) % acnt];
					if (x < y) edges_target[x][y] = 1; else edges_target[y][x] = 1;
				}
				for (i = 0; i < bcnt; i++) {
					int x = groupBp[i], y = groupBp[(i + 1) % bcnt];
					if (x < y) edges_target[x][y] = 1; else edges_target[y][x] = 1;
				}
				for (i = 1; i < N; i++) {
					for (j = i + 1; j <= N; j++) {
						if (edges[i][j] != edges_target[i][j]) score++;
					}
				}
				if (score < ans) ans = score;
			} while (next_permutation(groupBp + 1, bcnt - 1));
		} while (next_permutation(groupA + 1, acnt - 1));
	}
	printf("%d\n", ans);
	return 0;
}

/*

頂点数2で次数を2にしようとすると、多重辺にするしかない。
よって、目標のグラフの連結成分の頂点数は3以上。
N <= 8 なので、頂点数3以上のグループは高々2個しかできない。

*/

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