題目描述
請實現一個函數用來找出字符流中第一個只出現一次的字符。例如,當從字符流中只讀出前兩個字符"go"時,第一個只出現一次的字符是"g"。當從該字符流中讀出前六個字符“google"時,第一個只出現一次的字符是"l"。
輸出描述:
如果當前字符流沒有存在出現一次的字符,返回#字符。
import java.util.*;
public class Solution {
Queue<Integer> queue = new LinkedList<>();
int[] appeared = new int[256];
//Insert one char from stringstream
public void Insert(char ch) {
if (appeared[ch] == 0) {
appeared[ch] = 1;
queue.add((int) ch);
} else {
appeared[ch] = 2;
int size = queue.size();
while (size-- != 0) {
int peek = queue.peek();
if (appeared[peek] != 1) {
queue.remove();
} else {
break;
}
}
}
}
//return the first appearence once char in current stringstream
public char FirstAppearingOnce() {
int size = queue.size();
if (size == 0) {
return '#';
} else {
return (char) (int) queue.peek();
}
}
}