zoukankan      html  css  js  c++  java
  • [Leetcode 54] 49 Anagrams

    Problem:

    Given an array of strings, return all groups of strings that are anagrams.

    Note: All inputs will be in lower-case.

    Analysis:

    anagrams are those strings that consist of same characters but in different order. A very simple way to solve the problem is try to find each string's anagrams. This requires O(n^2) by scanning through the string vector and comparing the two sorted string whether are the same. But it won't work if the geiven string vector is too big.

    A O(n) solution is as follows: use a map structure to keep the pair of <string, vector<string>>, the key is the sorted string the value is the original string's vector. In this way, we only need scan through the string vector and the map to find all anagrams. The complecity is only O(n+m), n is ths string number and m is the map entry number.

    Code:

    O(n^2) solution, Time Limit Execeed under larger test case

     1 class Solution {
     2 public:
     3     vector<string> anagrams(vector<string> &strs) {
     4         // Start typing your C/C++ solution below
     5         // DO NOT write int main() function
     6         int tag[strs.size()];
     7         vector<string> mid;
     8         vector<string> res;
     9         
    10         res.clear();
    11         for (int i=0; i<strs.size(); i++) {
    12             tag[i] = 0;
    13             mid.push_back(strs[i]);
    14             sort(mid[i].begin(), mid[i].end());
    15         }
    16             
    17         for (int i=0; i<strs.size(); i++) {
    18             bool find = false;
    19             if (tag[i] == 0) {
    20                 for (int j=i+1; j<strs.size(); j++) {
    21                     if (tag[j] == 0 && mid[i] == mid[j]) {
    22                             res.push_back(strs[j]);
    23                             find = true;
    24                             tag[j] = 1;
    25                     }
    26                 }
    27                 
    28             }
    29             
    30             if (find) {
    31                 tag[i] = 1;
    32                 res.push_back(strs[i]);
    33             }
    34         }
    35         
    36         return res;
    37     }
    38 };
    View Code

    O(n) solution

     1 class Solution {
     2 public:
     3     vector<string> anagrams(vector<string> &strs) {
     4         // Start typing your C/C++ solution below
     5         // DO NOT write int main() function
     6         vector<string> res;
     7         map<string, vector<string> > sm; 
     8         
     9         for (int i=0; i<strs.size(); i++) {
    10             string s = strs[i];
    11             sort(s.begin(), s.end());
    12             sm[s].push_back(strs[i]);
    13         }
    14         
    15         for (map<string, vector<string> >::iterator it=sm.begin(); 
    16                     it!=sm.end(); it++) {
    17             if ((*it).second.size() >= 2) {
    18                 for (int i=0; i<(*it).second.size(); i++) {
    19                     res.push_back((*it).second[i]);
    20                 }
    21             }
    22         }
    23         
    24         return res;
    25     }
    26 };
    View Code
  • 相关阅读:
    网易2019校招C++研发工程师笔试编程题
    牛客网 数串
    ps aux 状态介绍
    阿里在线测评解析
    Ubuntu 18.04安装 Sublime
    file '/grub/i386-pc/normal.mod' not found.解决方案
    解决Windows10与Ubuntu系统时间不一致问题
    进程与线程的区别
    大端模式和小端模式
    2016湖南省赛----G
  • 原文地址:https://www.cnblogs.com/freeneng/p/3099602.html
Copyright © 2011-2022 走看看