資訊專欄INFORMATION COLUMN
摘要：用做，十分簡(jiǎn)單。如果不使用之外的數(shù)據(jù)結(jié)構(gòu)的話，可以用來(lái)做。不過(guò)只能過(guò)純字母字符的。
Problem
Implement an algorithm to determine if a string has all unique characters.
ExampleGiven "abc", return true.
Given "aab", return false.
ChallengeWhat if you can not use additional data structures?
Note用HashSet做，十分簡(jiǎn)單。
如果不使用String之外的數(shù)據(jù)結(jié)構(gòu)的話，可以用bit manipulation來(lái)做。不過(guò)只能過(guò)純字母字符的testcase。
public class Solution {
public boolean isUnique(String str) {
HashSet set = new HashSet();
for (int i = 0; i < str.length(); i++) {
if (!set.contains(str.charAt(i))) {
set.add(str.charAt(i));
}
else return false;
}
return true;
}
}
public class Solution {
public boolean isUnique(String s) {
int checker = 0;
for (int i = 0; i < s.length(); i++) {
int cur = s.charAt(i) - "a";
if ((checker & (1 << cur)) > 0) {
return false;
}
checker |= 1 << cur;
}
return true;
}
}
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