leetcode 904. 水果成篮

904. 水果成篮

说白了就是：找最多包含两种元素的最长子串，返回其长度

值得注意的是，当窗口内有三种种类时，左窗口边界是要向右移动到窗口内只剩两种种类，而不是什么先进先出！比如 [1,0,1,4,1,4,1,2,3] 

法一：unordered_map

class Solution {
public:
    int totalFruit(vector<int>& fruits) {
        int size = fruits.size(),resLenth = 0,left = 0,right;
        unordered_map<int,int> numAdded;
        for(right = 0;right < size;++right){
            if(numAdded.size() == 2 && numAdded.find(fruits[right]) == numAdded.end()){
                resLenth = max(resLenth,right - left);
                while(1){
                    --numAdded[fruits[left]];
                    if(numAdded[fruits[left]] == 0){
                        numAdded.erase(fruits[left]);
                        ++left;break;
                    }
                    ++left;
                }
            }
            ++numAdded[fruits[right]];
        }
        return max(resLenth,right - left);
    }
};

法二宫水三叶：不使用unordered_map，使用vector

class Solution {
public:
    int totalFruit(vector<int>& fruits) {
        int size = fruits.size(),resLenth = 0;
        vector<int> numAdded(size);
        for(int right = 0,left = 0,typeCount = 0;right < size;++right){
            ++numAdded[fruits[right]];
            if(numAdded[fruits[right]] == 1)  ++typeCount;//用typeCount表示当前加了多少个种类
            while(typeCount > 2){
                --numAdded[fruits[left]];
                if(numAdded[fruits[left]] == 0)  --typeCount;
                ++left;
            }
            resLenth = max(resLenth,right - left + 1);
        }
        return resLenth;
    }
};