[2021kakao-p4] 합승 택시 요금

Author: Seogeurim

Diff for: README.md

@@ -309,6 +309,12 @@
 
 ---
 
+## 2021 KAKAO BLIND RECRUITMENT
+
+|  #  |  ☆  | Problem                                                  | Note |
+| :-: | :-: | :------------------------------------------------------- | :--- |
+| 04  |     | [합승 택시 요금](./src/_2021_KAKAO_BLIND_RECRUITMENT/P4)    |      |
+
 ## 2020 KAKAO BLIND RECRUITMENT
 
 |  #  |  ☆  | Problem                                                  | Note |

Diff for: src/_2021_KAKAO_BLIND_RECRUITMENT/P4/Main.java

@@ -0,0 +1,50 @@
+package _2021_KAKAO_BLIND_RECRUITMENT.P4;
+
+public class Main {
+    public static void main(String[] args) {
+        Solution sol = new Solution();
+        System.out.println(sol.solution(6, 4, 6, 2,
+                new int[][]{{4, 1, 10}, {3, 5, 24}, {5, 6, 2}, {3, 1, 41}, {5, 1, 24}, {4, 6, 50}, {2, 4, 66}, {2, 3, 22}, {1, 6, 25}}));
+        System.out.println(sol.solution(7, 3, 4, 1,
+                new int[][]{{5, 7, 9}, {4, 6, 4}, {3, 6, 1}, {3, 2, 3}, {2, 1, 6}}));
+        System.out.println(sol.solution(6, 4, 5, 6,
+                new int[][]{{2,6,6}, {6,3,7}, {4,6,7}, {6,5,11}, {2,5,12}, {5,3,20}, {2,4,8}, {4,3,9}}));
+    }
+}
+
+class Solution {
+
+    final static int INF = Integer.MAX_VALUE;
+    static int[][] D;
+
+    public int solution(int n, int s, int a, int b, int[][] fares) {
+        D = new int[n+1][n+1];
+        for (int i = 1; i <= n; i++) {
+            for (int j = 1; j <= n; j++) {
+                if (i != j) D[i][j] = INF;
+            }
+        }
+
+        for (int[] fare : fares) {
+            int c = fare[0], d = fare[1], f = fare[2];
+            D[c][d] = f;
+            D[d][c] = f;
+        }
+
+        for (int k = 1; k <= n; k++) {
+            for (int i = 1; i <= n; i++) {
+                for (int j = 1; j <= n; j++) {
+                    if (D[i][k] == INF || D[k][j] == INF) continue;
+                    D[i][j] = Math.min(D[i][j], D[i][k] + D[k][j]);
+                }
+            }
+        }
+
+        int ans = D[s][a] + D[s][b];
+        for (int i = 1; i <= n; i++) {
+            ans = Math.min(ans, D[s][i] + D[i][a] + D[i][b]);
+        }
+
+        return ans;
+    }
+}

Diff for: src/_2021_KAKAO_BLIND_RECRUITMENT/P4/README.md

@@ -0,0 +1,5 @@
+## [2021 KAKAO BLIND RECRUITMENT - 4] 합승 택시 요금
+
+![image](https://user-images.githubusercontent.com/22045163/106773278-3d97b200-6684-11eb-983b-7ec540c30b44.png)
+
+문제를 읽어보면 최단 경로 문제이며, 경유지 K를 탐색하며 n의 크기가 작으므로 플로이드-워셜 알고리즘 문제임을 알 수 있다.