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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,79 @@ | ||
| package test.boj.dp; | ||
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| import org.junit.*; | ||
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| import java.io.*; | ||
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| import static org.assertj.core.api.Assertions.assertThat; | ||
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| public class o_계단_오르기 { | ||
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| public static void main(String[] args) throws IOException { | ||
| BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); | ||
| BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out)); | ||
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| int n = Integer.parseInt(br.readLine()); | ||
| int[] stairPoints = new int[n]; | ||
| for (int i = 0; i < n; i++) { | ||
| stairPoints[i] = Integer.parseInt(br.readLine()); | ||
| } | ||
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| Stairs stairs = new Stairs(n, stairPoints); | ||
| bw.write(String.valueOf(stairs.climb())); | ||
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| bw.flush(); | ||
| bw.close(); | ||
| br.close(); | ||
| } | ||
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| @Test | ||
| public void test() { | ||
| Stairs stairs = new Stairs(6, new int[]{10, 20, 15, 25, 10, 20}); | ||
| assertThat(stairs.climb()) | ||
| .isEqualTo(75); | ||
| } | ||
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| private static class Stairs { | ||
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| private static final int MAX_COUNT = 300; | ||
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| private final int[] stairPoints; | ||
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| private final int[] dp; | ||
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| public Stairs(int n, int[] stairPoints) { | ||
| this.stairPoints = new int[n + 1]; | ||
| this.dp = new int[MAX_COUNT + 1]; | ||
| for (int i = 1; i <= n; i++) { | ||
| this.stairPoints[i] = stairPoints[i - 1]; | ||
| } | ||
| } | ||
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| public int climb() { | ||
| dp[1] = this.stairPoints[1]; | ||
| dp[2] = dp[1] + this.stairPoints[2]; | ||
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| for (int i = 3; i < this.stairPoints.length; i++) { | ||
| dp[i] = Math.max(climbOneStair(i), climbTwoStair(i)); | ||
| } | ||
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| return dp[this.stairPoints.length - 1]; | ||
| } | ||
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| // 두 칸을 오르는 경우: 두 칸을 오르는 경우에는 3칸 연속 법칙이 성립할 수가 없음 | ||
| // 그러므로 두번 째 이전 칸에서의 최대 포인트과 현재 칸의 포인트를 더함 | ||
| private int climbTwoStair(int pos) { | ||
| if (pos < 3) throw new IllegalArgumentException(); | ||
| return this.stairPoints[pos] + this.dp[pos - 2]; | ||
| } | ||
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| // 한 칸을 오르는 경우: 3칸 연속 법칙 때문에 두번 째 이전 칸에 있는 계단과는 함께 오를 수 없음 | ||
| // 그러므로 현재 칸의 포인트와 이전 칸의 포인트를 더한 뒤 | ||
| // 세번 째 이전 칸에서의 최대 포인트와 더함 | ||
| private int climbOneStair(int pos) { | ||
| if (pos < 3) throw new IllegalArgumentException(); | ||
| return this.stairPoints[pos] + this.stairPoints[pos - 1] + this.dp[pos - 3]; | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,84 @@ | ||
| package test.boj.dp; | ||
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| import org.junit.*; | ||
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| import java.io.*; | ||
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| import static org.assertj.core.api.Assertions.assertThat; | ||
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| // https://cheolhojung.github.io/posts/algorithm/boj- sum-of-squares.html | ||
| public class p_제곱수의_합 { | ||
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| public static void main(String[] args) throws IOException { | ||
| BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); | ||
| BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out)); | ||
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| bw.write(String.valueOf(solution2(Integer.parseInt(br.readLine())))); | ||
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| bw.flush(); | ||
| bw.close(); | ||
| br.close(); | ||
| } | ||
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| @Test | ||
| public void test() { | ||
| // assertThat(solution2(7)) | ||
| // .isEqualTo(4); | ||
| // assertThat(solution2(11)) | ||
| // .isEqualTo(3); | ||
| // assertThat(solution2(12)) | ||
| // .isEqualTo(3); | ||
| // assertThat(solution2(100_000)) | ||
| // .isEqualTo(2); | ||
| // assertThat(solution2(10_000)) | ||
| // .isEqualTo(1); | ||
| assertThat(solution2(142)) | ||
| .isEqualTo(3); | ||
| } | ||
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| private static int solution2(int n) { | ||
| int [] dp = new int[n + 1]; | ||
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| for(int i = 1; i <= n; i++) { | ||
| dp[i] = i; | ||
| for(int j = 1, pow = j * j; pow <= i; j++, pow = j * j) | ||
| if(dp[i] > dp[i - pow] + 1) | ||
| dp[i] = dp[i - pow] + 1; | ||
| } | ||
| return dp[n]; | ||
| } | ||
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| // n이 제곱이면 dp[n] = 2 | ||
| // n이 제곱이 아니라면, (n - i => i) dp[n] = min((dp[n - 1] + dp[1]) .... dp[n - i] + dp[i]) | ||
| private static int solution(int n) { | ||
| final int MAX_SQUARE = 100_001; | ||
| final int MAX_SQRT = (int) Math.sqrt(MAX_SQUARE); | ||
| boolean[] isSquare = new boolean[MAX_SQUARE]; | ||
| int[] dp = new int[n + 1]; | ||
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| isSquare[1] = true; | ||
| dp[1] = 1; | ||
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| for (int i = 2; i <= n; i++) { | ||
| if (isSquare[i]) { | ||
| dp[i] = 1; | ||
| } else { | ||
| dp[i] = getMin(dp, i); | ||
| } | ||
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| if (i <= MAX_SQRT) { | ||
| isSquare[i * i] = true; | ||
| } | ||
| } | ||
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| return dp[n]; | ||
| } | ||
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| private static int getMin(int[] dp, int n) { | ||
| int min = Integer.MAX_VALUE; | ||
| for (int i = 1; n - i >= i; i++) { | ||
| min = Math.min(min, dp[n - i] + dp[i]); | ||
| } | ||
| return min; | ||
| } | ||
| } |