leetcode-25-exercise_string&array
14. Longest Common Prefix
Write a function to find the longest common prefix string amongst an array of strings.
解题思路:
以strs[0]为标准,LCP的长度必不超过strs[0]的长度,从前向后遍历。内层遍历所有的串,如果在所有串中都有strs[0][i],
就把它放到result中,否则返回。
string longestCommonPrefix(vector<string>& strs) { int len = strs.size(); string result = ""; if (len == 0) return result; if (len == 1) return strs[0]; if (strs[0] == "") return strs[0]; for (int i = 0; i < strs[0].length(); i++) { for (int j = 1; j < len; j++) { if (strs[j].length() == i || strs[0][i] != strs[j][i]) return result; } result.push_back(strs[0][i]); } return result; }
219. Contains Duplicate II
Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j] and the absolute difference between i and j is at most k.
解题思路:
使用unordered_map存储<nums[i], first_i>。如果当前i-first_i <= k,那就找到了。
bool containsNearbyDuplicate(vector<int>& nums, int k) { if (k == 0) return false; unordered_map<int, int> m; for (int i = 0; i < nums.size(); i++) { if (m.find(nums[i]) != m.end() && i - m[nums[i]] <= k) return true; else m[nums[i]] = i; } return false; }