Best Time to Buy and Sell Stock II--疑惑

https://oj.leetcode.com/problems/best-time-to-buy-and-sell-stock-ii/

代码如下时能AC

 1 class Solution {
 2 public:
 3     int maxProfit(vector<int> &prices) {
 4         int p=0;
 5         for(int i = 1; i < prices.size() ; ++i) {
 6             int delta = prices[i] - prices[i-1];
 7             if(delta > 0 ) {
 8                 p += delta;
 9             }
10         }
11         return p;
12     }
13 };

但是，代码如下时却Runtime Error,提示Last executed input:[]

 1 class Solution {
 2 public:
 3     int maxProfit(vector<int> &prices) {
 4         int p=0;
 5         for(int i = 0; i < prices.size()-1 ; ++i) {
 6             int delta = prices[i+1] - prices[i];
 7             if(delta > 0 ) {
 8                 p += delta;
 9             }
10         }
11         return p;
12     }
13 };

这代码明明跟这段Java是一样的啊。这Java代码也能AC。奇怪。

1 public class Solution {
2 public int maxProfit(int[] prices) {
3     int total = 0;
4     for (int i=0; i< prices.length-1; i++) {
5         if (prices[i+1]>prices[i]) total += prices[i+1]-prices[i];
6     }
7 
8     return total;
9 }

最后只能是加入一行

1  if(prices.size()==0) return 0;

来保证edge case.

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This problem is solved by Shangrila finally:

Replace prices.size()-1 by int(prices.size())-1. The type of prices.size() is SIZE_T, which is unsigned integer types. -1 could overflow.

answered 9 hours ago by Shangrila (48,010 points)