LeetCode 3

Posted 2020-07-09 Juntaran

Longest Substring Without Repeating Characters

Given a string, find the length of the longest substring
without repeating characters.

Examples:

Given "abcabcbb", the answer is "abc", which the length is 3.

Given "bbbbb", the answer is "b", with the length of 1.

Given "pwwkew", the answer is "wke", with the length of 3.
Note that the answer must be a substring,
"pwke" is a subsequence and not a substring.

 

 1 /*************************************************************************
 2     > File Name: LeetCode003.c
 3     > Author: Juntaran
 4     > Mail: [email protected]
 5     > Created Time: Tue 17 May 2016 17:10:02 PM CST
 6  ************************************************************************/
 7 
 8 /*************************************************************************
 9     
10     Longest Substring Without Repeating Characters
11     
12     Given a string, find the length of the longest substring 
13     without repeating characters.
14 
15     Examples:
16 
17     Given "abcabcbb", the answer is "abc", which the length is 3.
18 
19     Given "bbbbb", the answer is "b", with the length of 1.
20 
21     Given "pwwkew", the answer is "wke", with the length of 3. 
22     Note that the answer must be a substring, 
23     "pwke" is a subsequence and not a substring.
24 
25  ************************************************************************/
26 
27 #include "stdio.h"
28 
29 /* 8ms */
30 int lengthOfLongestSubstring(char* s)
31 {
32     int n = strlen(s);
33     
34     if( n <= 1 )
35     {
36         return n;
37     }
38     
39     int i = 0, j = 0;
40     int maxLen = 0;
41     int exist[256] = { 0 };
42     while( j < n )
43     {
44         if( exist[s[j]] )
45         {
46             maxLen = maxLen>(j-i) ? maxLen : (j-i);
47             while( s[i] != s[j] )
48             {
49                 exist[s[i]] = 0;
50                 i++;
51             }
52             i++;
53             j++;
54         }
55         else
56         {
57             exist[s[j]] = 1;
58             j++;
59         }
60     }
61     maxLen = maxLen>(n-i) ? maxLen : (n-i);
62     return maxLen;
63 }
64 
65 /* 36ms */
66 int lengthOfLongestSubstring2(char* s)
67 {
68     int len = 0;
69     int p=0 , q=0,  i; 
70 
71     for( q=0; q<strlen(s); q++ )
72     {
73         for( i=p; i<q; i++ )
74         {
75             if( s[q] == s[i] )
76             {
77                 if( q-p > len ) len = q-p;
78                 p = i+1;
79             }
80         }
81     }
82     len = len>q-p?len:q-p;
83     return len;
84 }
85 
86 int main()
87 {
88     char* s = "abccab";
89     int ret = lengthOfLongestSubstring(s);
90     printf("%d\n", ret);
91     
92     return 0;
93 }