文章目录
一、题目
121. Best Time to Buy and Sell Stock
You are given an array prices where prices[i] is the price of a given stock on the ith day.
You want to maximize your profit by choosing a single day to buy one stock and choosing a different day in the future to sell that stock.
Return the maximum profit you can achieve from this transaction. If you cannot achieve any profit, return 0.
Example 1:
Input: prices = [7,1,5,3,6,4]
Output: 5
Explanation: Buy on day 2 (price = 1) and sell on day 5 (price = 6), profit = 6-1 = 5.
Note that buying on day 2 and selling on day 1 is not allowed because you must buy before you sell.
Example 2:
Input: prices = [7,6,4,3,1]
Output: 0
Explanation: In this case, no transactions are done and the max profit = 0.
Constraints:
1 <= prices.length <= 105
0 <= prices[i] <= 104
题目来源：leetcode
二、题解
使用动态规划的思想，避免双重for循环，在O(n)时间内解决问题
cpp
class Solution {
public:
int max(int a,int b){
if(a > b) return a;
else return b;
}
int maxProfit(vector<int>& prices) {
const int N = 100010;
int n = prices.size();
int dp[N];
dp[0] = 0;
int minVal = prices[0];
for(int i = 1;i < n;i++){
if(prices[i] < minVal) minVal = prices[i];
dp[i] = max(prices[i] - minVal,dp[i-1]);
}
return dp[n-1];
}
};