2020.7.13

 

350. 两个数组的交集 II

哈希表 

public class Solution {
    public int[] intersect(int[] nums1, int[] nums2) {
        if(nums1.length > nums2.length) return intersect(nums2, nums1);
        if(nums1.length <= 0) return new int[0];
        Map<Integer, Integer> map = new HashMap<Integer, Integer>();
        for(int num : nums1){
            int count = map.getOrDefault(num, 0) + 1;
            map.put(num, count);
        }
        int[] result = new int[nums1.length];
        int index = 0;
        for(int num : nums2){
            int count = map.getOrDefault(num, 0);
            if (count > 0) {
                result[index++] = num;
                if(--count > 0){
                    map.put(num, count);
                }else {
                    map.remove(num);
                }
            }
        }
        return Arrays.copyOfRange(result, 0 , index);
    }
}

from typing import List
from collections import Counter


class Solution:
    def intersect(self, nums1: List[int], nums2: List[int]) -> List[int]:
        if len(nums1) > len(nums2):
            return self.intersect(nums2, nums1)
        if len(nums1) <= 0:
            return []

        ct1 = Counter(nums1)
        res = list()
        for num in nums2:
            count = ct1.get(num, 0)
            if count > 0:
                res.append(num)
                ct1[num] -= 1
                if count <= 0:
                    ct1.pop(num)
        return res


nums1 = [1, 2, 2, 1]
nums2 = [2, 2]
s = Solution()
print(s.intersect(nums1, nums2))

7. 整数反转

class Solution {
  public int reverse(int x) {
        int flag = 1;
        long xx = x;
        if(x < 0) {
            flag = -1;
            xx *= flag;
        }
        String str = String.valueOf(xx);
        StringBuffer stb = new StringBuffer(str.length());
        for (int i = str.length() - 1; i >= 0 ; i--) {
            stb.append(str.charAt(i));
        }
        long y = Long.parseLong(stb.toString());
        if(y > Integer.MAX_VALUE  ||  y * flag < Integer.MIN_VALUE  )
            flag = 0;
        return (int)(flag * y);
    }

}

class Solution:
        def reverse(self, x: int) -> int:
            flag = 1
            if x < 0:
                flag = -1
                x *= flag
            y = str(x)[::-1]
            res = int(y)
            if (-2)**31 > res * flag or flag * res > 2**31-1:
                flag = 0
            return flag * res