九日集训 Day6 贪心

段过 2022-04-21 23:59:19

0.两个数对之间的最大乘积差

class Solution {
public:
    int maxProductDifference(vector<int>& nums) {
        sort(nums.begin(),nums.end());
        int sz =nums.size();
        return nums[sz-1]*nums[sz-2]-nums[0]*nums[1];
    }
};

1.三角形的最大周长

class Solution {
public:
    int largestPerimeter(vector<int>& nums) {
        sort(nums.begin(),nums.end());
        for(int i=nums.size()-1;i>=2;i--){
            if(nums[i-1]+nums[i-2]>nums[i]){
                return nums[i-1]+nums[i-2]+nums[i];
            }
        }
        return 0;
    }
};

2.数组拆分 I

class Solution {
public:
    int arrayPairSum(vector<int>& nums) {
        sort(nums.begin(),nums.end());
        int sz=nums.size();
        int minsum=0;
        for(int i=0;i<sz;i+=2)
        {
            minsum+=nums[i];
        }
        return minsum;
    }
};

3.救生艇

class Solution {
public:
    int numRescueBoats(vector<int>& people, int limit) {
        int sz =people.size();
        sort(people.begin(),people.end());
        auto l=0;
        auto r=sz-1;
        int amount=0;
        while(l<=r)
        {
            if(l==r)
            {
                amount++;
                break;
            }
            else if(people[l]+people[r]>limit)
            {
                amount++;
                r--;
            }
            else
            {
                amount++;
                l++; r--;
            }
        }
        return amount;
    }
};

4.摆动排序 II

class Solution {
public:
    void wiggleSort(vector<int>& nums) {
        int sz=nums.size();
        int r=sz-1;
        sort(nums.begin(),nums.end());
        vector<int> ans=nums;
        for(int i=1;i<sz;i+=2)
        {
            nums[i]=ans[r--];
        }
        for(int i=0;i<sz;i+=2)
        {
            nums[i]=ans[r--];
        }
    }
};

n/2 < n > n/2+1 < n-1 > .........n/2-1 >0

5.分发饼干

class Solution {
public:
    int findContentChildren(vector<int>& g, vector<int>& s) {
        int g_sz=g.size(); int s_sz=s.size();
        int ans=0;
        int i=g_sz-1, j=s_sz-1;
        sort(g.begin(),g.end());
        sort(s.begin(),s.end());
        while(i>=0&&j>=0)
        {  
            if(s[j]>=g[i])
            {
                ++ans;
                --i, --j;
            }
            else
            {
                --i;
            }
        }
        return ans;
    }
};

6.最少操作使数组递增

class Solution {
public:
    int minOperations(vector<int>& nums) {
        int sz=nums.size();
        int ans=0;
        for(int i=1;i<sz;++i)
        {
            if(nums[i]<=nums[i-1])
            {
                ans+= nums[i-1]-nums[i]+1;
                nums[i]=nums[i-1]+1;
            }
        }
        return ans;
    }
};

7.使数组唯一的最小增量

类似上一题，不过要先排序

class Solution {
public:
    int minIncrementForUnique(vector<int>& nums) {
        int sz=nums.size();
        sort(nums.begin(),nums.end());
        int ans=0;
        for(int i=1;i<sz;++i)
        {
            if(nums[i]<=nums[i-1])
            {
                ans+= nums[i-1]-nums[i]+1;
                nums[i]=nums[i-1]+1;
            }
        }
        return ans;
    }
};