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Longest Substring Without Repeating Characters
Given a string, find the length of the longest substring without repeating characters.
Example 1:
Input: "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.
Example 2:
Input: "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.
Example 3:
Input: "pwwkew"
Output: 3
Explanation: 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.
my solution
class Solution {
public int lengthOfLongestSubstring(String s) {
if (s.length() == 0){
return 0;
}
int curhead = 0;
int curlength = 1;
int maxlength = 1;
Map<Character, Integer> charLocation= new HashMap<>();
charLocation.put(s.charAt(curhead),curhead);
for (int i = 1; i < s.length(); ++i){
int oldloc = -1;
if(charLocation.containsKey(s.charAt(i))){
oldloc = charLocation.get(s.charAt(i));
}
if(oldloc < curhead){
curlength++;
maxlength = maxlength>curlength?maxlength:curlength;
}else{
curhead = oldloc+1;
curlength = i-oldloc;
}
charLocation.put(s.charAt(i),i);
}
return maxlength;
}
}
逻辑清晰一点的解法:
public class Solution {
public int lengthOfLongestSubstring(String s) {
int n = s.length(), ans = 0;
Map<Character, Integer> map = new HashMap<>(); // current index of character
// try to extend the range [i, j]
for (int j = 0, i = 0; j < n; j++) {
if (map.containsKey(s.charAt(j))) {
i = Math.max(map.get(s.charAt(j)), i);
}
ans = Math.max(ans, j - i + 1);
map.put(s.charAt(j), j + 1);
}
return ans;
}
}
或者用int array 替代 hashmap
public class Solution {
public int lengthOfLongestSubstring(String s) {
int n = s.length(), ans = 0;
int[] index = new int[128]; // current index of character
// try to extend the range [i, j]
for (int j = 0, i = 0; j < n; j++) {
i = Math.max(index[s.charAt(j)], i);
ans = Math.max(ans, j - i + 1);
index[s.charAt(j)] = j + 1;
}
return ans;
}
}