[s1]

트리 구조에서, "최소"의 집합을 계속 올려가야 하므로 dp 개념이라는 것을 기억하기

Ssafy_test/src/BOJ/silver1/BOJ_1149.java

@@ -1,10 +1,61 @@
 package BOJ.silver1;
 
-public class BOJ_1149 {
-
-	public static void main(String[] args) {
-		// TODO Auto-generated method stub
+import java.util.*;
+import java.io.*;
 
+public class BOJ_1149 {
+	static int iNum;
+	static int[][] dp;
+	static int[][] ll;
+
+	public static int DP(int i, int j) {
+		if(dp[i][j] != 0) { //저장된 수가 있음
+			return dp[i][j];
+		}
+
+		int m = 0;
+
+		if(j == 0) {
+			m = Math.min(DP(i+1,1), DP(i+1,2));
+		}else if(j == 1) {
+			m = Math.min(DP(i+1,0), DP(i+1,2));
+		}else { //j == 2
+			m = Math.min(DP(i+1,0), DP(i+1,1));
+		}
+
+		dp[i][j] = m + ll[i][j];
+
+		return dp[i][j];
+	}
+
+	public static void main(String[] args) throws IOException{
+		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+		BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+
+		iNum = Integer.parseInt(br.readLine());
+		dp = new int[iNum][3];
+		ll = new int[iNum][3];
+
+		for(int i = 0; i<iNum; i++) {
+			StringTokenizer st = new StringTokenizer(br.readLine());
+			for(int j = 0; j<3; j++) {
+				ll[i][j] = Integer.parseInt(st.nextToken());
+			}
+		}
+
+		//초기화
+		dp[iNum-1][0] = ll[iNum-1][0];
+		dp[iNum-1][1] = ll[iNum-1][1];
+		dp[iNum-1][2] = ll[iNum-1][2];
+
+		int ans = Integer.MAX_VALUE;
+		for(int i = 0; i<3; i++) {
+			ans = Math.min(ans,DP(0, i));
+		}
+
+		bw.write(ans + "\n");
+		bw.flush();
+		br.close();
+		bw.close();
 	}
-
 }