LeetCode-Best Time to Buy and Sell Stock III算法对比

LeetCode 123.Best Time to Buy and Sell Stock III

由于先做了这类题目的 I II，看到III就直接按照先求局部最大值，取最大的前两个的和。（错误的代码就不贴了。。。）后来一直wrong answer. 忽然明白了限定两手交易，仍然可能将两个局部最大值连起来组成更大数值。一时想不起来解法

看到两个算法：

1.大牛1用分治策略，移动分割点分别计算左右最大值。再加上优化就过了！http://blog.csdn.net/littlestream9527/article/details/21326153

2.在这里 http://www.tuicool.com/articles/JjAnue。 看到代码吃了一惊！大神真是兼备简要的代码而又清晰的思路。拜大神！ -~-~-~-~-

原帖在github上 https://github.com/zhumeng1989/MISC/blob/nightly/common/leetcode.hpp#L611
// 123.Best Time to Buy and Sell Stock III

class Solution {

public:

  int maxProfit(vector &prices) {

    int maxval = 0;

    int n = prices.size();

    if (n <= 1) return 0;

    int curmin = prices[0];

    vector l2r(n,0);

    for (int i=1; i

      curmin = min(curmin, prices[i]);

      maxval = max(maxval, prices[i]-curmin);

      l2r[i] = maxval;

    }

    maxval = 0;

    int curmax = prices[n-1];

    vector r2l(n,0);

    for (int i=n-2; i>=0; i--) {

      curmax = max(curmax, prices[i]);

      maxval = max(maxval, curmax-prices[i]);

      r2l[i] = maxval;

    }

    maxval = 0;

    for (int i=0; i

      maxval = max(maxval, l2r[i]+r2l[i]);

    return maxval;

  }

};