class Solution { public: int vis[3][3]; int ans[10]; int dir[16][2] = { //16个方向 { -1, 0 }, { -1, 1 }, { 0, 1 }, { 1, 1 }, { 1, 0 }, { 1, -1 }, { 0, -1 }, { -1, -1 }, {-2, 1 }, { -1, 2 }, { 1, 2 }, { 2, 1 }, { 2, -1 }, { 1, -2 }, { -1, -2 }, { -2, -1 } }; void dfs(int x, int y, int t) { if (9 == t) { return; } ans[t++]++; vis[x][y] = 1; for (int i = 0; i < 16; i++) { int dx = x + dir[i][0]; int dy = y + dir[i][1]; if (0 <= dx && dx < 3 && dy >= 0 && dy < 3 && vis[dx][dy] == 0) { dfs(dx, dy, t); } //如果前8个方向都走过了，可以沿着当前方向在走一步 else if (i < 8) { dx = dx + dir[i][0]; dy = dy + dir[i][1]; if (0 <= dx && dx < 3 && dy >= 0 && dy < 3 && vis[dx][dy] == 0) { dfs(dx, dy, t); } } } vis[x][y] = 0; return; } int solution(int m, int n) { memset(ans, 0, sizeof(ans)); for (int i = 0; i < 3; i++) { for (int j = 0; j < 3; j++) { memset(vis, 0, sizeof(vis)); dfs(i, j, 1); } } int num = 0; if (m > n) return 0; else { if (n > 9) n = 9; ans[9] = ans[8]; for (int i = m; i <= n; i++) { num = num + ans[i]; } return num; } } };
https://www.nowcoder.com/questionTerminal/c552248efdbd41a18d35b7a2329f7ad8