【LC刷题】DAY24：122 55 45 1005

122. 买卖股票的最佳时机 II

class Solution {
public:
    int maxProfit(vector<int>& prices) {
        int result = 0;
        for(int i = 1; i < prices.size(); i ++){
            result += max(prices[i] - prices[ i - 1], 0);
        }
        return result;
    }
};

55. 跳跃游戏 link

class Solution {
public:
    bool canJump(vector<int>& nums) {
        int cover = 0;
        if(nums.size() == 1) return true;
        for(int i = 0; i <= cover; i ++){
            cover = max(i + nums[i], cover);
            if(cover >= nums.size() - 1)return true;
        }
        return false;
    }
};

45. 跳跃游戏 II link

class Solution {
public:
    int jump(vector<int>& nums) {
        if(nums.size() == 1) return 0;
        int curDistance = 0;
        int ans = 0;
        int nextDistance = 0;
        for(int i = 0; i < nums.size(); i ++){
            nextDistance = max(nums[i] + i,  nextDistance);
            if(i == curDistance){
                ans ++;
                curDistance = nextDistance;
                if(nextDistance >= nums.size() - 1)  break;
            }
        }
        return ans;
    }
};

1005. K 次取反后最大化的数组和 link

class Solution {
public:
    static bool cmp(int a, int b){
        return abs(a) > abs(b);
    }
    int largestSumAfterKNegations(vector<int>& nums, int k) {
        sort(nums.begin(), nums.end(), cmp);
        for(int i = 0; i < nums.size(); i ++){
            if(nums[i] < 0 && k > 0){
                nums[i] *= -1;
                k --;
            }
        }
        if(k % 2 == 1) nums[nums.size() -1] *= -1;
        int result = 0;
        for(int a: nums) result += a;
        return result;
    }
};