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LeetCode Best Time to Buy and Sell Stock IV

时间:2015-04-06 15:27:02      阅读:202      评论:0      收藏:0      [点我收藏+]

Say you have an array for which the ith element is the price of a given stock on day i.

Design an algorithm to find the maximum profit. You may complete at most k transactions.

 

Solution:

典型的 dynamic programming

当 k(k=1000000000)很大时 申请过多内存会发生 runtime error 

分两类情况处理。

 1  int maxProfit(int k, vector<int> &prices) {
 2        if (k > (prices.size() >> 1)) {
 3             int maxm = 0;
 4             for (int i = 0; i < (int)prices.size() - 1; ++i) {
 5                 if (prices[i+1] > prices[i]) {
 6                     maxm += prices[i+1] - prices[i];
 7                 }
 8             }
 9     
10             return maxm;
11         }
12         else {
13             int *dp = new int [((k << 1) | 1)];
14             dp[0] = 0;
15             for (int i = 1; i <= (k<<1); ++i) {
16                 dp[i] = INT_MIN;
17             }
18             for (int i = 0; i < prices.size(); ++i) {
19                 for (int j = min(i+1, k<<1); j >= 1; --j) {
20                     int v = j & 0x01 ? -prices[i] : prices[i];
21                      dp[j] = max(dp[j], dp[j-1] + v);
22                 }
23             }
24             int maxm = 0;
25             for (int i = 1; i <= (k<<1); ++i) {
26                 maxm = max(maxm, dp[i]);
27             }
28     
29             delete[] dp;
30             return maxm;
31         }

 

LeetCode Best Time to Buy and Sell Stock IV

原文:http://www.cnblogs.com/liew/p/4395948.html

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