数组拷贝，二分法查找

Posted 2021-03-26

Arrays.copyOfRange(int[] arr,int开始下标，int结束下标)//左闭右开 System.arraycopy（int[] source,int开始下标，int[] dest,int开始下标，int拷贝多少个） 这里是手动拷贝： public static int[] copyOf(int[] original, int newLength) { int[] dest = new int[newLength]; int length = original.length <= newLength ? original.length : newLength; for (int i = 0; i < length; i++) { dest[i] = original[i]; } return dest; } mid作为分水岭， 不断地缩小范围 // 前提需要数组是有序的 public static int binarySearch(int[] a, int v) { int left = 0; int right = a.length; while (left < right) { int mid = (left + right) / 2; if (v == a[mid]) { return mid; } else if (v < a[mid]) { right = mid; } else { left = mid + 1; } } return -1; } public static int binarySearch2(int[] a, int v) { int left = 0; int right = a.length - 1; while (left <= right) { int mid = (left + right) / 2; if (v == a[mid]) { return mid; } else if (v < a[mid]) { right = mid - 1; } else { left = mid + 1; } } return -1; }