代码随想录算法训练营第二十九天|134 加油站、135 分发糖果、860 柠檬水找零、406 根据身高重建队列

一、134 加油站

class Solution {
public:
    int canCompleteCircuit(vector<int>& gas, vector<int>& cost) {
        int start = 0;
        int cursum = 0;
        int totalsum = 0;
        for(int i=0;i<gas.size();i++){
            cursum += (gas[i] - cost[i]);
            totalsum += (gas[i] - cost[i]);
            if(cursum < 0){
                start = i+1;
                cursum = 0;
            }
        }
        if(totalsum < 0)
            return -1;
        return start;
    }
};

二、135 分发糖果

class Solution {
public:
    int candy(vector<int>& ratings) {
        vector<int> candyVec(ratings.size(), 1);//保存ratings.size个1
        int i;
        int result = 0;
        //右>左
        for(i = 1;i<ratings.size();i++){//从第二个元素开始
            if(ratings[i]>ratings[i-1]){
                candyVec[i] = candyVec[i-1]+1;
            }
        }
        //左>右
        for(i = ratings.size()-2;i>=0;i--){//从倒数第二个元素开始
            if(ratings[i]>ratings[i+1]){
                candyVec[i] = max(candyVec[i+1]+1,candyVec[i]);//取两种情况都满足的值
            }
        }
        for(i = 0;i<candyVec.size();i++){
            result += candyVec[i];
        }
        return result;
    }
};

三、860 柠檬水找零

class Solution {
public:
    bool lemonadeChange(vector<int>& bills) {
        int five = 0;
        int ten = 0;
        int twenty = 0;
        for(int bill:bills){
            if(bill == 5)
                five++;
            if(bill == 10){
                if(five <= 0)
                    return false;
                ten++;
                five--;
            }
            if(bill == 20){
                if(ten>0&&five>0){
                    ten--;
                    five--;
                    twenty++;
                }
                else if(ten<=0&&five>=3){
                    five -= 3;
                    twenty++;
                }
                else
                    return false;
            }
        }
        return true;
    }
};

四、406 根据身高重建队列

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);//按照身高从大到小，身高一样则按k从小到大排序
        vector<vector<int>>queue;
        for(int i = 0;i<people.size();i++){
            int pos = people[i][1];
            queue.insert(queue.begin()+pos,people[i]);
        }
        return queue;
    }
};