Find the Difference(leetcode389)

Given two strings s and t which consist of only lowercase letters.

String t is generated by random shuffling string s and then add one more letter at a random position.

Find the letter that was added in t.

Example:

Input:
s = "abcd"
t = "abcde"

Output:
e

Explanation:
'e' is the letter that was added.

 

//既然都是小寫字母 那麼用以前的數組也是解決的
//這種方法與使用map是相同的
public static char findTheDifference(String s, String t) {

    int[] arr = new int[26];
    for (int i = 0; i < t.length(); i++) {
        arr[t.charAt(i) - 'a']++;
    }
    for (int i = 0; i < s.length(); i++) {
       --arr[s.charAt(i)-'a'];
    }
    for (int i =0;i< arr.length;i++){
        if(arr[i]>0){
            return (char)(i+'a');
        }

    }
    return ' ';
}

 

//原來還能夠這麼寫呀
public static char findTheDifference2(String s, String t) {
    char c = 0;
    for (int i = 0; i < s.length(); ++i) {
        c ^= s.charAt(i);
    }
    for (int i = 0; i < t.length(); ++i) {
        c ^= t.charAt(i);
    }
    return c;
}

 

//寫的看上去簡略一點 少循環一次
public static char findTheDifference3(String s, String t) {
    int n = t.length();
    char c = t.charAt(n - 1);
    for (int i = 0; i < n - 1; ++i) {
        c ^= s.charAt(i);
        c ^= t.charAt(i);
    }
    return c;
}

 

git：https://github.com/woshiyexinjie/leetcode-xin