DAY31|455.分发饼干 、376. 摆动序列 、53. 最大子序和

455.分发饼干 

class Solution {
public:
    int findContentChildren(vector& g, vector& s) {
        sort(g.begin(), g.end());//排序胃口
        sort(s.begin(), s.end());//排序饼干大小
        int index = s.size() - 1; //index等于饼干的最大值的下标
        int result = 0;//记录满足几个孩子
        for(int i = g.size() - 1;i >= 0; i--){ //遍历胃口
            if(index >= 0 && s[index] >= g[i]) 
            {
                result ++;
                index --;
            }
        }
        return result;
    }
};

376. 摆动序列 

class Solution {
public:
    int wiggleMaxLength(vector& nums) {
        if(nums.size() <= 1) return nums.size(); 
        int curDiff = 0;
        int preDiff = 0;
        int length = 1;
        for(int i = 0;i < nums.size() - 1;i++){
            curDiff = nums[i + 1] - nums[i];
            if((curDiff > 0 && preDiff <=0) || (curDiff < 0 && preDiff >=0)){
                 length ++;
                 preDiff = curDiff;
            }
           
        }
        return length;
    }
};

53. 最大子序和

暴力解法  ，超时。

class Solution {
public:
    int maxSubArray(vector& nums) {
        int result = INT32_MIN;
        int count = 0;
        for (int i = 0; i < nums.size(); i++) { // 设置起始位置
            count = 0;
            for (int j = i; j < nums.size(); j++) { // 每次从起始位置i开始遍历寻找最大值
                count += nums[j];
                result = count > result ? count : result;
            }
        }
        return result;
    }
};

贪心算法

class Solution {
public:
    int maxSubArray(vector& nums) {
        int count = 0;
        int result = INT32_MIN;
        if(nums.size() <= 1) return nums[0];
        for (int i = 0; i < nums.size(); i++) { // 设置起始位置
            count = count + nums[i];
            if(count > result){
                result = count;
            }
            if (count <= 0) count = 0; 
        }
        return result;
    }
};