# Leetcode 904. Fruit Into Baskets
###### tags: `leetcode` `daily` `Sliding window` `two pointer`

[題目連結](https://leetcode.com/problems/fruit-into-baskets/description/)

# Method Sliding Window
:::info
:bulb: **作法講解**:
step 1, we are maintaing window, initially size is 1, that means start=0, end=0
we using hash_map to record each element in current window at fruits.

step 2, scan each index end in fruits,
increment the count of hash_map with key is fruit[end],
when hash_map size is over than 2,
we move start to the next element,
in the meantime, decrement the count of hash_map with key is fruit[start].
candidate of output is length between start to end
:::

TC: O(N) SC: O(1)
:::spoiler 完整程式碼

class Solution {
public:
    int totalFruit(vector<int>& fruits) {
        int n = fruits.size();
        int l = 0;
        int output = 0;
        unordered_map<int, int> m;

        for(int i = 0 ; i < n ; i++) {
            m[fruits[i]]++;

            while(m.size() > 2) {
                m[fruits[l]]--;
                if(m[fruits[l]] == 0) {
                    m.erase(fruits[l]);
                }
                l++;
            }
            output = max(output, i - l + 1);
        }

        return output;
    }
};

:::