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-rw-r--r--painting_grid_three_colour.cpp58
1 files changed, 0 insertions, 58 deletions
diff --git a/painting_grid_three_colour.cpp b/painting_grid_three_colour.cpp
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--- a/painting_grid_three_colour.cpp
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-// 1931. Painting a Grid With Three Different Colors
-#include "leetcode.h"
-
-/*
- * given two integers 'm' and 'n'. consider an 'm x n' grid where each cell is
- * initially white. you can painteach cell red, green, or blue. all cells must
- * be painted. return the number of ways to colour the grid with no two adjacent
- * cells having the same colour.
- */
-
-class Solution {
- int memo[1000][1024] = {};
- vector<int> nei_memo[1024] = {};
- int m, n, mod = 1e9 + 7;
- int dp(int c, int prev) {
- if (c == n)
- return 1;
- if (memo[c][prev])
- return memo[c][prev];
- int res = 0;
- for (int nei : neighbours(prev))
- res = (res + dp(c + 1, nei)) % mod;
- return memo[c][prev] = res;
- }
- vector<int> neighbours(int prev) {
- if (!nei_memo[prev].empty())
- return nei_memo[prev];
- dfs(0, prev, 0, nei_memo[prev]);
- return nei_memo[prev];
- }
- void dfs(int r, int prev, int curr, vector<int> &out) {
- if (r == m) {
- out.push_back(curr);
- return;
- }
- for (int i = 0; i <= 3; i++)
- if (get_colour(prev, r) != i && (!r || get_colour(curr, r - 1) != i))
- dfs(r + 1, prev, set_colour(curr, r, i), out);
- }
- int get_colour(int mask, int pos) { return (mask >> (2 * pos)) & 3; }
- int set_colour(int mask, int pos, int colour) {
- return mask | (colour << (2 * pos));
- }
-
-public:
- int colorTheGrid(int m, int n) {
- this->m = m;
- this->n = n;
- return dp(0, 0);
- }
-};
-
-int main() {
- Solution obj;
- printf("%d\n", obj.colorTheGrid(1, 1)); // expect: 3
- printf("%d\n", obj.colorTheGrid(1, 2)); // expect: 6
- printf("%d\n", obj.colorTheGrid(5, 5)); // expect: 580986
-}