题解 | #字符流中第一个不重复的字符#

import java.util.*;
public class Solution {

    private int[] arr = new int[128];
    private int index = 0;
    //Insert one char from stringstream
    public void Insert(char ch){
        if(arr[ch] == 0){
            index++;
            arr[ch] = index;
        } else{
            arr[ch] = -1;
        }

    }
  //return the first appearence once char in current stringstream
    public char FirstAppearingOnce(){
        int min = Integer.MAX_VALUE;
        char result = '#';
        for(int i = 0;i<arr.length;i++){
            if(arr[i] > 0 && arr[i] < min){
                min = arr[i];
                result = (char)i;
            }
        }
        return result;
    }
}