add PROGRAMMERS-12979

Author: codejsha

README.md

@@ -18,6 +18,7 @@
 | PROGRAMMERS-12951         | [java](programmers/problem12951)   | [JadenCase 문자열 만들기 (JadenCase String)](https://school.programmers.co.kr/learn/courses/30/lessons/12951)                         |
 | PROGRAMMERS-12953 :star:  | [java](programmers/problem12953)   | [N개의 최소공배수 (N Least Common Multiple)](https://school.programmers.co.kr/learn/courses/30/lessons/12953)                         |
 | PROGRAMMERS-12973         | [java](programmers/problem12973)   | [짝지어 제거하기 (Elimination by Grouping)](https://school.programmers.co.kr/learn/courses/30/lessons/12973)                          |
+| PROGRAMMERS-12979         | [java](programmers/problem12979)   | [기지국 설치 (Base Station Installation)](https://school.programmers.co.kr/learn/courses/30/lessons/12979)                            |
 | PROGRAMMERS-12980         | [java](programmers/problem12980)   | [점프와 순간 이동 (Jump and Teleport)](https://school.programmers.co.kr/learn/courses/30/lessons/12980)                               |
 | PROGRAMMERS-12981         | [java](programmers/problem12981)   | [영어 끝말잇기 (English Word Relay)](https://school.programmers.co.kr/learn/courses/30/lessons/12981)                                 |
 | PROGRAMMERS-12985 :star:  | [java](programmers/problem12985)   | [예상 대진표 (Expected List of Matches)](https://school.programmers.co.kr/learn/courses/30/lessons/12985)                             |

programmers/problem12979/BaseStationInstallation.java

@@ -0,0 +1,54 @@
+package problem12979;
+
+public class BaseStationInstallation {
+    public static void main(String[] args) {
+        var sol = new BaseStationInstallation();
+        var n1 = 11;
+        var stations1 = new int[]{4, 11};
+        var w1 = 1;
+        var expected1 = 3;
+        var result1 = sol.solution(n1, stations1, w1);
+        System.out.println("test1: expected: " + expected1 + ", result: " + result1);
+        var n2 = 16;
+        var stations2 = new int[]{9};
+        var w2 = 2;
+        var expected2 = 3;
+        var result2 = sol.solution(n2, stations2, w2);
+        System.out.println("test2: expected: " + expected2 + ", result: " + result2);
+    }
+
+    private static int needStationCount(int n, int w) {
+        return (int) Math.ceil((double) n / (2 * w + 1));
+    }
+
+    public int solution(int n, int[] stations, int w) {
+        if (stations.length == 0) {
+            return needStationCount(n, w);
+        }
+
+        var needCount = 0;
+        var index = 0;
+        var boundary = stations[index] - w;
+        var shadow = 1;
+
+        while (true) {
+            if (boundary - shadow > 0) {
+                needCount += needStationCount(boundary - shadow, w);
+            }
+            shadow = boundary + 2 * w + 1;
+            if (shadow > n) {
+                break;
+            }
+
+            if (index < stations.length - 1) {
+                index++;
+                boundary = stations[index] - w;
+            } else {
+                needCount += needStationCount(n - shadow + 1, w);
+                break;
+            }
+        }
+
+        return needCount;
+    }
+}