2024/11/22 灵茶题单 二分查找

src/main/java/com/cool/ling_cha_mount/binary_search/Num658.java

@@ -0,0 +1,87 @@
+package com.cool.ling_cha_mount.binary_search;
+
+import org.junit.Test;
+
+import java.util.*;
+
+public class Num658 {
+
+
+    public List<Integer> findClosestElements1(int[] arr, int k, int x) {
+        int size = arr.length;
+        int left = 0;
+        int right = size - k;
+        while (left < right) {
+            // int mid = left + (right - left) / 2;
+            int mid = (left + right) / 2;
+            // 尝试从长度为 k + 1 的连续子区间删除一个元素
+            // 从而定位左区间端点的边界值
+            if (x - arr[mid] > arr[mid + k] - x) {
+                // 下一轮搜索区间是 [mid + 1..right]
+                left = mid + 1;
+            } else {
+                // 下一轮搜索区间是 [left..mid]
+                right = mid;
+            }
+        }
+
+        List<Integer> res = new ArrayList<>();
+        for (int i = left; i < left + k; i++) {
+            res.add(arr[i]);
+        }
+        return res;
+    }
+
+    public List<Integer> findClosestElements(int[] arr, int k, int x) {
+        int i = binarySearch(arr, x);
+        if (i < 0) {
+            List<Integer> list = new ArrayList<>();
+            for (int j = 0; j < k; j++) {
+                list.add(arr[j]);
+            }
+            return list;
+        }
+        int left = i;
+        int right = i+1;
+        List<Integer> list = new ArrayList<>();
+        while (k > 0) {
+            if (right < arr.length && left >= 0) {
+                if (x - arr[left] >= arr[right] - x) {
+                    list.add(arr[right]);
+                    right++;
+                } else {
+                    list.add(arr[left]);
+                    left--;
+                }
+            } else if (right < arr.length) {
+                list.add(arr[right]);
+                right++;
+            } else {
+                list.add(arr[left]);
+                left--;
+            }
+            k--;
+        }
+        list.sort(Comparator.comparing((a) -> a));
+        return list;
+    }
+
+    private int binarySearch(int[] nums, int target) {
+        int left = -1;
+        int right = nums.length;
+        while (left + 1 < right) {
+            int mid = (left + right) >>> 1;
+            if (target < nums[mid]) {
+                right = mid;
+            } else {
+                left = mid;
+            }
+        }
+        return left;
+    }
+
+    @Test
+    public void test() {
+        findClosestElements(new int[]{1,1,1,10,10,10}, 1, 9);
+    }
+}