121. Best Time to Buy and Sell Stock

Say you have an array for which the ith element is the price of a given stock on day i. If you were only permitted to complete at most one transaction (i.e., buy one and sell one share of the stock), design an algorithm to find the maximum profit.

class Solution {
    public int maxProfit(int[] prices) {
        // set dp[i] = the max profix of subarray start from 0 end at index i
        // int min = the minimal vale of subarray start from 0 end at index i-1
        // dp[i] = Math.max(dp[i-1], prices[i]-min);
        
        if (prices.length<1) return 0;
        
        // initialize the base case
        // for i =0, dp[i]=0
        int min = prices[0];
        prices[0]=0;
        for (int i=1; i<prices.length; i++){
            int temp = prices[i];
            prices[i] = Math.max(prices[i-1], prices[i]-min);
            min = temp<min? temp: min;
        }
        return prices[prices.length-1];
    }
}