买卖股票的最佳时机
动态规划
class Solution {
public int maxProfit(int[] prices) {
int n = prices.length;
int sum =0;
int start = prices[0];
for(int i =1;i<n;i++){
if(prices[i] - start >0){
if(sum <prices[i] - start)
sum = prices[i] - start;
}else{
start = prices[i];
}
}
return sum;
}
}