算法60天：day35

贪心算法-柠檬水找零

力扣链接

class Solution {
public:
    bool lemonadeChange(vector<int>& bills) {
        //第一种情况：收到5元，five++
        //第二种情况：收到10元，five--，ten++
        //第三种情况：收到20元，优先消耗10元
        int five = 0, ten = 0, twenty = 0;
        for(int i = 0; i < bills.size(); i++){
            if(bills[i] == 5){
                five++;
            }else if(bills[i] == 10){
                if(five <= 0) return false;
                five--;
                ten++;
            }else if(bills[i] == 20){
                if(ten > 0 && five > 0){
                    ten--;
                    five--;
                    twenty++;
                }else if(five >= 3){
                    five -= 3;
                    twenty++;
                }else{
                    return false;
                }
            }
        }
        return true;
    }
};

贪心算法-根据身高重建队列

力扣链接

class Solution {
public:
    static bool cmp(const vector<int>& a, const vector<int>& b){
        if(a[0] == b[0]) return a[1] < b[1];
        return a[0] > b[0];
    }
    vector<vector<int>> reconstructQueue(vector<vector<int>>& people) {
        sort(people.begin(),people.end(),cmp);
        vector<vector<int>> que;
        for(int i = 0; i < people.size(); i++){
            int index = people[i][1];
            que.insert(que.begin() + index, people[i]);
        }
        return que;
    }
};

贪心算法-用最少数量的箭引爆气球

力扣链接

class Solution {
public:
    //降序排序
    static bool cmp(vector<int>& a, vector<int>& b){
        return a[0] < b[0];
    }
    int findMinArrowShots(vector<vector<int>>& points) {
        if(points.size() == 1) return 1;
        //先排序
        sort(points.begin(),points.end(),cmp);
        //记录箭数
        int result = 1;
        for(int i = 1; i < points.size(); i++){
            if(points[i][0] > points[i - 1][1]){    //当前气球的左边界大于前一个气球的有边界，所以两个气球不相邻
                result++;
            }else{
                points[i][1] = min(points[i][1] , points[i - 1][1]);    //设置当前气球的右边界为该区间右值最小
            }
        }
        return result;
    }
};