class Solution {
public int[] twoSum(int[] nums, int target) {
HashMap<Integer,Integer> map=new HashMap<>();
for(int i=0;i<nums.length;i++){
if(map.containsKey(target-nums[i]))
return new int[]{i,map.get(target-nums[i])};
map.put(nums[i],i);
}
return null;
}
}
map.getOrDefault() 获取map中指定key的value值, 若不存在设为一个default值
class Solution {
public int firstUniqChar(String s) {
HashMap<Character,Integer> map=new HashMap<>();
for(int i=0;i<s.length();i++){
Character c=s.charAt(i);
map.put(c,map.getOrDefault(c,0)+1);
}
int result=0;
for(int i=0;i<s.length();i++){
Character c=s.charAt(i);
if(map.get(c)==1)
return i;
}
return -1;
}
}