[DP] baekjoon-2098

Author: Seogeurim

README.md

@@ -376,6 +376,7 @@
 | 30  |     | [SWEA-1861 정사각형 방](src/DP/swea1861)                    |        |
 | 31  |     | [SWEA-1952 수영장](src/DP/swea1952)                        |        |
 | 32  |     | [JUNGOL-1681 해밀턴 순환회로](./src/DP/jo1681)               |  TSP  |
+| 33  |     | [Baekjoon-2098 외판원 순회](./src/DP/P2098)                 |  TSP  |
 
 ## Time Complexity
 

src/DP/P2098/Main.java

@@ -0,0 +1,45 @@
+package DP.P2098;
+
+import java.io.*;
+import java.util.*;
+
+public class Main {
+
+    static int INF = 160000000;
+    static int N;
+    static int[][] W, dp;
+
+    public static void main(String[] args) throws Exception {
+        System.setIn(new FileInputStream("src/DP/P2098/input.txt"));
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+
+        N = Integer.parseInt(br.readLine());
+        W = new int[N][N];
+        for (int i = 0; i < N; i++) {
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            for (int j = 0; j < N; j++) {
+                W[i][j] = Integer.parseInt(st.nextToken());
+            }
+        }
+
+        dp = new int[1<<N][N];
+        for (int i = 0; i < 1 << N; i++) Arrays.fill(dp[i], INF);
+
+        System.out.println(TSP(1, 0));
+    }
+
+    static int TSP(int mask, int now) {
+        if (mask == (1<<N)-1) {
+            if (W[now][0] > 0) return W[now][0];
+            return INF;
+        }
+
+        if (dp[mask][now] != INF) return dp[mask][now];
+        for (int i = 0; i < N; i++) {
+            if ((mask & 1<<i) == 0 && W[now][i] > 0) {
+                dp[mask][now] = Math.min(dp[mask][now], TSP(mask|1<<i, i) + W[now][i]);
+            }
+        }
+        return dp[mask][now];
+    }
+}

src/DP/P2098/README.md

@@ -0,0 +1,26 @@
+## [baekjoon-2098] 외판원 순회
+
+![image](https://user-images.githubusercontent.com/22045163/112101265-b37ebb00-8be9-11eb-8302-789243835946.png)
+
+### 외판원 순회 문제
+
+외판원 순회 문제는 비트마스크 + DP 를 이용한 문제이다. 풀이 및 코드를 이해한 후, 외우는 것이 좋은 것 같다.
+
+```java
+int TSP(int mask, int now) {
+    if (mask == (1<<N)-1) {
+        if (W[now][0] > 0) return W[now][0];
+        return INF;
+    }
+
+    if (dp[mask][now] != INF) return dp[mask][now];
+    for (int i = 0; i < N; i++) {
+        if ((mask & 1<<i) == 0 && W[now][i] > 0) {
+            dp[mask][now] = Math.min(dp[mask][now], TSP(mask|1<<i, i) + W[now][i]);
+        }
+    }
+    return dp[mask][now];
+}
+```
+
+![image](https://user-images.githubusercontent.com/22045163/112101291-bc6f8c80-8be9-11eb-97ee-5add4fa8208f.png)

src/DP/P2098/input.txt

@@ -0,0 +1,5 @@
+4
+0 10 15 20
+5 0 9 10
+6 13 0 12
+8 8 9 0