資訊專欄INFORMATION COLUMN
Problem
Given a string, find the first non-repeating character in it and return it"s index. If it doesn"t exist, return -1.
ExampleGiven s = "lintcode", return 0.
Given s = "lovelintcode", return 2.
TagsAmazon Microsoft Bloomberg
Solutionclass Solution {
public int firstUniqChar(String s) {
int[] dict = new int[26];
for (int i = 0; i < s.length(); i++) {
dict[s.charAt(i)-"a"]++;
}
for (int i = 0; i < s.length(); i++) {
if (dict[s.charAt(i)-"a"] == 1) return i;
}
return -1;
}
}
public class Solution {
public int firstUniqChar(String s) {
//store string in an array
char[] str = s.toCharArray();
//use HashMap to check each character"s frequency
Map map = new HashMap<>();
for (int i = 0; i < str.length; i++) {
char ch = str[i];
//reset duplicate chars to "#"
if (map.containsKey(ch)) {
str[map.get(ch)] = "#";
str[i] = "#";
} else {
map.put(ch, i);
}
}
int index = str.length;
for (int i = 0; i < str.length; i++) {
//find the first character that is not "#" and return its index
if (str[i] != "#") {
return i;
}
}
//if no unique character, return -1
return -1;
}
}
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