11.5 Given a sorted array of strings which is interspersed with empty strings, write a method to find the location of a given string.
EXAMPLE
Input: find "ball" in {"at", "", "", "", "ball", "", "", "car", "", "", "dad", "", ""}
Output: 4
这道题给了我们一个有序的字符串数组，但是在中间加入了很多空字符串，让我们来查找一个给定字符串。如果没有这些空字符串，那么我们用二分查找法很容易搜索，但是这些空字符串就有很大的干扰作用。那么我们要在原有的二分查找法上做修改，类似的修改二分查找法的里有Search in Rotated Sorted Array 在旋转有序数组中搜索和Search in Rotated Sorted Array II 在旋转有序数组中搜索之二。这道题我们的思路是，查找中间的字符串，如果是空字符串，那么我们用二分查找法来找周围最近的非空字符串，然后把mid移到飞空字符串的位置，继续二分查找。相当于二分查找中又嵌套了一个二分查找，参见代码如下：
class Solution { public: int search(vector<string> strings, string str) { int first = 0, last = strings.size() - 1; while (first <= last) { int mid = first + (last - first) / 2; if (strings[mid].empty()) { int left = mid - 1, right = mid + 1; while (true) { if (left < first && right > last) return -1; else if (right <= last && !strings[right].empty()) { mid = right; break; } else if (left >= first && !strings[left].empty()) { mid = left; break; } ++right; --left; } } int res = strings[mid].compare(str); if (res == 0) return mid; else if (res < 0) first = mid + 1; else last = mid - 1; } return -1; } };
本文转自博客园Grandyang的博客，原文链接：搜索含有空字符串的数组[CareerCup] 11.5 Search Array with Empty Strings ，如需转载请自行联系原博主。