122. Best Time to Buy and Sell Stock II

Input: prices = [7,1,5,3,6,4]
Output: 7
Explanation: Buy on day 2 (price = 1) and sell on day 3 (price = 5), profit = 5-1 = 4.
Then buy on day 4 (price = 3) and sell on day 5 (price = 6), profit = 6-3 = 3.
Input: prices = [1,2,3,4,5]
Output: 4
Explanation: Buy on day 1 (price = 1) and sell on day 5 (price = 5), profit = 5-1 = 4.
Note that you cannot buy on day 1, buy on day 2 and sell them later, as you are engaging multiple transactions at the same time. You must sell before buying again.
Input: prices = [7,6,4,3,1]
Output: 0
Explanation: In this case, no transaction is done, i.e., max profit = 0.
class Solution {
public:
int maxProfit(vector<int>& prices) {
int len = prices.size();
int min_p = 0;
int max_p = 0;
int ans = 0;
for(int i=0; i<len; i++){
while(i+1<len && prices[i+1] < prices[i]){
i++;
}
min_p = prices[i];
while(i+1<len && prices[i+1] > prices[i]){
i++;
}
max_p = prices[i];
ans += max_p - min_p;
}
return ans;

}
};

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