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leetcode----Longest Substring Without Repeating Characters

2015-12-11 16:52 1231 查看

C++ code in 9 lines

int lengthOfLongestSubstring(string s) {
vector<int> dict(256, -1);
int maxLen = 0, start = -1;
for (int i = 0; i != s.length(); i++) {
if (dict[s[i]] > start)
start = dict[s[i]];
dict[s[i]] = i;
maxLen = max(maxLen, i - start);
}
return maxLen;
}

O(n) time O(1) space solution using Kadane's algo in Java

public class Solution {
public int lengthOfLongestSubstring(String s) {
int lastIndices[] = new int[256];
for(int i = 0; i<256; i++){
lastIndices[i] = -1;
}
int maxLen = 0;
int curLen = 0;
int start = 0;
int bestStart = 0;
for(int i = 0; i<s.length(); i++){
char cur = s.charAt(i);
if(lastIndices[cur] < start){
lastIndices[cur] = i;
curLen++;
} else{
int lastIndex = lastIndices[cur];
start = lastIndex+1;
curLen = i-start+1;
lastIndices[cur] = i;
}if(curLen > maxLen){
maxLen = curLen;
bestStart = start;
}
} return maxLen;
}
}

Share my Java solution using HashSet

public int lengthOfLongestSubstring(String s) {
int i = 0, j = 0, max = 0;
Set<Character> set = new HashSet<>();
while (j < s.length()) {
if (!set.contains(s.charAt(j))) {
set.add(s.charAt(j++));
max = Math.max(max, set.size());
} else {
set.remove(s.charAt(i++));
}
} return max;
}
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标签:  leetcode C++ java