二刷34.|二刷34. Search for a Range 二刷34.SearchforaRange

【二刷34.|二刷34. Search for a Range】出 bug的地方：

一开始没判断nums == null || nums.length == 0
二分搜索的时候有可能start就没找到，这个时候start=first会导致start = -1后面你用nums[start]就会数组越界. 所以搜索完start的时候你要记得判断一下start == -1?如果等于说明nums里面没有target你要直接返回[-1,-1]

class Solution { public int[] searchRange(int[] nums, int target) { if (nums == null || nums.length == 0){ return new int[]{-1,-1}; } //[1] //0 int first = -1; int last = -1; int start = 0; int end = nums.length - 1; while (start + 1 < end){ int mid = start + (end - start) / 2; if (nums[mid] >= target){ end = mid; } else { start = mid; } } if (nums[start] == target){ first = start; } else if (nums[end] == target){ first = end; } start = first; end = nums.length - 1; if (start == -1){ return new int[]{-1,-1}; } while (start + 1 < end){ int mid = start + (end - start) / 2; if (nums[mid] <= target){ start = mid; } else { end = mid; } } if (nums[end] == target){ last = end; } else if (nums[start] == target){ last = start; } return new int[]{first, last}; } }