关于 Java 中的最大值/利润子数组问题的问题

Question

这是数组...int[] array = new int[]{4,-1,-2,3,5,-7,1,0,0,-2,4};我们需要看看我们是否可以从前一天开始购买股票。因此，我们应该以 -1 的价格买入并以 5 的价格卖出。这将带来 6 的利润。    int max = Integer.MIN_VALUE;    int maxDiff = Integer.MIN_VALUE;    int diff = 0;    int bottom = array[0];    for (int i = 1; i < array.length; i++) {        diff += array[i] - array[i - 1];        System.out.println(diff);        if (diff > maxDiff) {            maxDiff = diff;            max = array[i];        }        if (array[i] < bottom) {            bottom = array[i];            diff = 0;        }    }    int maxx = max - maxDiff;    System.out.println("Buy at " + maxx + " Sell at " + max);这就是说我应该在 -7 买入并在 4 卖出。这是不正确的。如果我们在 -7 买入，价格将上涨 1，然后保持不变，保持不变，下跌 2，然后上涨 4。这不会为我们赚取最大利润。我究竟做错了什么？

Answer 1

由于数组包含价格变动，因此假设起始价格并从中计算最小/最大值

int max = Integer.MIN_VALUE;

int min = Integer.MAX_VALUE;

int price = 100;

int dayIn = 0;

int dayOut = 0;

for (int i = 0; i < array.length; i++) {

    price += array[i];

    if (price > max) {

        max = price;

        dayOut = i;

    } 

    if (price < min) {

        min = price;

        dayIn = i;

    } 

}

if (max > min && dayIn < dayOut) { 

    System.out.printf("Buy for %d at day %d and sell on day %d for %d. Profit: %d\n", min, (dayIn + 1), (dayOut+1), max, max - min);

} else {

    System.out.println("No trade opportunity found");

}