[2020kakao(intern)-p4] 경주로 건설

Author: Seogeurim

README.md

@@ -518,3 +518,4 @@
 | 01  |     | [키패드 누르기](./src/_2020_카카오_인턴십/P1)       |      |
 | 02  |     | [수식 최대화](./src/_2020_카카오_인턴십/P2)         |  구현  |
 | 03  |     | [보석 쇼핑](./src/_2020_카카오_인턴십/P3)          |  2-pointer |
+| 04  |     | [경주로 건설](./src/_2020_카카오_인턴십/P4)          |  dfs + dp  |

src/_2020_카카오_인턴십/P4/Main.java

@@ -0,0 +1,65 @@
+package _2020_카카오_인턴십.P4;
+
+public class Main {
+
+    public static void main(String[] args) {
+        Solution sol = new Solution();
+        System.out.println(sol.solution(new int[][]{{0,0,0},{0,0,0},{0,0,0}}));
+        System.out.println(sol.solution(new int[][]{{0,0,0,0,0,0,0,1},{0,0,0,0,0,0,0,0},{0,0,0,0,0,1,0,0},{0,0,0,0,1,0,0,0},{0,0,0,1,0,0,0,1},{0,0,1,0,0,0,1,0},{0,1,0,0,0,1,0,0},{1,0,0,0,0,0,0,0}}));
+        System.out.println(sol.solution(new int[][]{{0,0,1,0},{0,0,0,0},{0,1,0,1},{1,0,0,0}}));
+        System.out.println(sol.solution(new int[][]{{0,0,0,0,0,0},{0,1,1,1,1,0},{0,0,1,0,0,0},{1,0,0,1,0,1},{0,1,0,0,0,1},{0,0,0,0,0,0}}));
+    }
+}
+
+class Solution {
+
+    int N;
+    int[] di = {-1, 0, 1, 0}, dj = {0, 1, 0, -1};
+    int[][] board, dp;
+
+    public int solution(int[][] board) {
+
+        N = board.length;
+        this.board = board;
+        dp = new int[N][N];
+
+        for (int i = 0; i < N; i++) {
+            for (int j = 0; j < N; j++) {
+                dp[i][j] = Integer.MAX_VALUE;
+            }
+        }
+
+        dp[0][0] = 0;
+        for (int d = 1; d <= 2; d++) dfs(0, 0, d);
+
+//        for (int i = 0; i < N; i++) {
+//            for (int j = 0; j < N; j++) {
+//                if (dp[i][j] == Integer.MAX_VALUE) System.out.print("INF ");
+//                else System.out.print(dp[i][j] + " ");
+//            }
+//            System.out.println();
+//        }
+
+        return dp[N-1][N-1];
+    }
+
+    void dfs(int i, int j, int d) {
+        if (i == N-1 && j == N-1) return;
+
+        for (int k = 0; k < 4; k++) {
+            int to_i = i + di[k];
+            int to_j = j + dj[k];
+
+            int plus = d == k ? 100 : 600;
+            if (isValidPath(to_i, to_j) && board[to_i][to_j] == 0 && dp[to_i][to_j] >= dp[i][j]+plus) {
+//                System.out.println(i + " " + j + " | to: " + to_i + " " + to_j + " | d : " + d + " k : " + k + " | cost : " + (dp[i][j]+plus));
+                dp[to_i][to_j] = dp[i][j]+plus;
+                dfs(to_i, to_j, k);
+            }
+        }
+    }
+
+    boolean isValidPath(int i, int j) {
+        return 0 <= i && i < N && 0 <= j && j < N;
+    }
+}

src/_2020_카카오_인턴십/P4/README.md

@@ -0,0 +1,3 @@
+## [2020 카카오 인턴십] 경주로 건설
+
+![image](https://user-images.githubusercontent.com/22045163/116574247-82ac4700-a948-11eb-81a2-3873eb8e1ba7.png)