【剑指Offer】34、第一个只出现一次的字符

 1  public static int FirstNotRepeatingChar(String str) {
 2         Map<Character, Integer> map = new HashMap<>();
 3         if(str==null){
 4             return 0;
 5         }
 6         char[] chars = str.toCharArray();
 7         int len=chars.length;
 8         for(int i=0;i<len;i++){
 9             if(map.containsKey(str.charAt(i))){
10                 int time = map.get(str.charAt(i));
11                 map.put(str.charAt(i), ++time);
12             }else {
13                 map.put(str.charAt(i), 1);
14             }
15         }
16         int index = -1;
17         for( int i=0;i<str.length();i++){
18             char c = str.charAt(i);
19             if (map.get(c) == 1) {
20                 return i;
21             }
22         }
23         return index;
24     }

 1 public static int FirstNotRepeatingChar01(String str){
 2         char[] chars = str.toCharArray();
 3         int[] map = new int[256];
 4         for (int i = 0; i < chars.length; i++) {
 5             map[chars[i]]++;
 6         }
 7         //遍历一遍字符串，找出第一个数组内容为1的字母
 8         for (int i = 0; i < chars.length; i++) {
 9             if (map[chars[i]] == 1){
10                 return i;
11             }
12         }
13         return -1;
14     }

1 public static void main(String[] args) {
2         String str="google";
3         int index = FirstNotRepeatingChar01(str);
4         System.out.println(index);
5     }
6 输出：4