Problem:
You’re given strings J representing the types of stones that are jewels, and S representing the stones you have. Each character in S is a type of stone you have. You want to know how many of the stones you have are also jewels. The letters in J are guaranteed distinct, and all characters in J and S are letters. Letters are case sensitive, so “a” is considered a different type of stone from “A”.
Example 1:
Input: J = “aA”, S = “aAAbbbb” Output: 3
Example 2:
Input: J = “z”, S = “ZZ” Output: 0
Note:
思路: 记录J的信息,遍历S,采用Hashmap的思路,每次查询O(1),总时间复杂度为O(n)
Java版本:
public int numJewelsInStones(String J, String S) {
int[] count = new int[64];
for (char c : J.toCharArray()) {
count[c - 'A']++;
}
int ans = 0;
for (char c : S.toCharArray()) {
if (count[c - 'A'] >= 1) ans ++;
}
return ans;
}
Python版本:
class Solution(object):
def numJewelsInStones(self, J, S):
"""
:type J: str
:type S: str
:rtype: int
"""
info = set(J)
ans = 0
for c in S:
if c in info: ans += 1
return ans
再精简一波:
class Solution(object):
def numJewelsInStones(self, J, S):
"""
:type J: str
:type S: str
:rtype: int
"""
info = set(J)
return sum(c in info for c in S)