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84 lines
2.2 KiB
84 lines
2.2 KiB
package class_2022_09_4_week;
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// 给你两个整数 m 和 n 。构造一个 m x n 的网格，其中每个单元格最开始是白色
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// 请你用 红、绿、蓝 三种颜色为每个单元格涂色。所有单元格都需要被涂色
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// 涂色方案需要满足：不存在相邻两个单元格颜色相同的情况
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// 返回网格涂色的方法数。因为答案可能非常大
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// 返回 对 109 + 7 取余 的结果。
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// 1 <= n <= 1000
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// 1 <= m <= 5
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// 测试链接 : https://leetcode.cn/problems/painting-a-grid-with-three-different-colors/
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public class Code04_PaintingGridWithThreeDifferentColors {
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// public static int zuo(int i, int j, int s, int n, int m) {
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// if (i == n) {
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// return 1;
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// }
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// if (j == m) {
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// return zuo(i + 1, 0, s, n, m);
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// }
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//
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// // j列
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// int up = (s >> (j * 2)) & 3;
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// int left = j == 0 ? 0 : ((s >> ((j - 1) * 2)) & 3);
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// int ans = 0;
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// if (up != 1 && left != 1) { // 当前格子就涂1这个颜色
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// int exp = statu
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// ans += zuo( i, j + 1, ?, n,m);
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//
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// }
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// if (up != 2 && left != 2) {
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//
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// }
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// if (up != 3 && left != 3) {
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//
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// }
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// return ans;
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// }
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public static final int mod = 1000000007;
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public static int colorTheGrid(int m, int n) {
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int status = 1 << (m << 1);
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int[][][] dp = new int[n][m][status];
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for (int i = 0; i < n; i++) {
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for (int j = 0; j < m; j++) {
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for (int s = 0; s < status; s++) {
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dp[i][j][s] = -1;
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}
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}
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}
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return process(0, 0, 0, n, m, dp);
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}
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public static int process(int i, int j, int s, int n, int m, int[][][] dp) {
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if (i == n) {
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return 1;
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}
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if (j == m) {
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return process(i + 1, 0, s, n, m, dp);
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}
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if (dp[i][j][s] != -1) {
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return dp[i][j][s];
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}
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int up = (s >> (j * 2)) & 3;
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int left = j == 0 ? 0 : ((s >> ((j - 1) << 1)) & 3);
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int ans = 0;
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if (up != 1 && left != 1) {
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ans += process(i, j + 1,(s ^ (up << (j * 2))) | (1 << (j * 2)), n, m, dp);
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ans %= mod;
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}
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if (up != 2 && left != 2) {
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ans += process(i, j + 1, (s ^ (up << (j << 1))) | (2 << (j << 1)), n, m, dp);
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ans %= mod;
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}
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if (up != 3 && left != 3) {
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ans += process(i, j + 1, (s ^ (up << (j << 1))) | (3 << (j << 1)), n, m, dp);
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ans %= mod;
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}
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dp[i][j][s] = ans;
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return ans;
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}
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}
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