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  • [LeetCode] Best Time to Buy and Sell Stock III

    Personally, this is a relatively difficult DP problem. This link posts a typical DP solution to it. You may need some time to get how it works.

    The code is rewritten as follows.

     1 class Solution {
     2 public:
     3     int maxProfit(vector<int>& prices) {
     4         int n = prices.size(), num = 2;
     5         if (n <= 1) return 0;
     6         vector<vector<int> > dp(num + 1, vector<int>(n, 0));
     7         for (int k = 1; k <= num; k++) {
     8             int temp = dp[k - 1][0] - prices[0];
     9             for (int i = 1; i < n; i++) {
    10                 dp[k][i] = max(dp[k][i - 1], prices[i] + temp);
    11                 temp = max(temp, dp[k - 1][i] - prices[i]);
    12             }
    13         }
    14         return dp[num][n - 1];
    15     }
    16 };

    Personally, I prefer this solution, which is much easier to understand. The code is also rewritten as follows.

    class Solution {
    public:
        int maxProfit(vector<int>& prices) {
            int states[2][4] = {INT_MIN, 0, INT_MIN, 0};
            int n = prices.size(), cur = 0, next = 1;
            for (int i = 0; i < n; i++) {
                states[next][0] = max(states[cur][0], -prices[i]);
                states[next][1] = max(states[cur][1], states[cur][0] + prices[i]);
                states[next][2] = max(states[cur][2], states[cur][1] - prices[i]);
                states[next][3] = max(states[cur][3], states[cur][2] + prices[i]);
                swap(cur, next);
            }
            return max(states[cur][1], states[cur][3]);
        }
    };
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  • 原文地址:https://www.cnblogs.com/jcliBlogger/p/4699326.html
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