Wins the second edition offer - face questions 63 (java)

Interview questions: the largest share of the profits

topic:

It is assumed that a stock's price in chronological order stored in an array, what's largest trading profits once the stock is likely to get much

Such as: a stock price for some time node} {9,11,8,5,7,12,16,14, if sold in May to buy 16, the maximum profit gains 11

Ideas:

Stock Trading profits from buying and selling shares of the difference, and can only sell after buying

If the bid and ask price of two digits of a number, the number of profit is the difference

The maximum profit is the difference between the maximum number of array all right

First, the solution can be violent - find all logarithm, differencing one by one, the time complexity of O (n)

two,

Defined maximum profit when selling price is the i-th array numbers may be obtained when the fixed selling price, the lower the price the greater the profit to buy

That is, if the array is scanned to the i-th digit, the minimum value of i-1 digits before long as we can remember is, you can calculate the maximum profit at the current selling price is likely to get

Code:

public class Q63 {
	public static void main(String[] args) {
		int[] a = new int[] {9,11,8,5,7,12,16,14};
		int re = maxDiff(a);
		System.out.println(re);
	}
	
	public static int maxDiff(int[] a) {
		if(a.length<2) {
			System.out.println("wrong input");
			return 0;
		}
		
		int min = a[0];
		int max = a[1]-a[0];
		
		for(int i=1;i<a.length;i++) {
			// 记录差值最大值
			if(a[i]-min>max) {
				max = a[i]-min;
			}
			
			// 记录最小值
			if(a[i]<min) {
				min = a[i];
			}				
		}
		return max;
	}
}