acadia/c++/algorithm/misc/StockBuySell.cpp at master · billyean/acadia · GitHub

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//Copyright [2018] [Haibo Yan]
//
//Licensed under the Apache License, Version 2.0 (the "License");
//you may not use this file except in compliance with the License.
//You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
//Unless required by applicable law or agreed to in writing, software
//distributed under the License is distributed on an "AS IS" BASIS,
//WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//See the License for the specific language governing permissions and
//limitations under the License.

//
// Created by haibo on 3/19/18.
//

#include "StockBuySell.h"
#include <algorithm>

int StockBuySell::maxProfitI(vector<int>& prices) {
    int maxProfit = 0;

    if (prices.size() > 1) {
        int minPrice = prices[0];

        for (int i = 1; i < prices.size(); i++) {
            maxProfit = max(maxProfit, prices[i] - minPrice);
            minPrice = min(minPrice, prices[i]);
        }
    }

    return maxProfit;
}

int StockBuySell::maxProfitII(vector<int>& prices) {
    int maxProfit = 0;

    if (prices.size() > 1) {
        int minPrice = prices[0];

        for (int i = 0; i < prices.size() - 1; i++) {
            if (prices[i + 1] > prices[i]) {
                maxProfit += prices[i + 1] - prices[i];
            }
        }
    }

    return maxProfit;
}

int StockBuySell::maxProfitIII(vector<int>& prices) {
    int maxProfit = 0;

    if (prices.size() > 1) {
        int lastIndex = prices.size() - 1;
        int left[prices.size()], right[prices.size()];
        int minLeft = left[0] = 0;
        int minRight = right[lastIndex] = 0;

        for (int i = 1; i < prices.size(); i++) {
            left[i] = max(left[i - 1], prices[i] - minLeft);
            minLeft = min(minLeft, prices[i]);

            right[lastIndex - i] = max(right[lastIndex - i], prices[i] - minRight);
            minRight = min(minRight, prices[lastIndex - i]);
        }

        for (int i = 0; i < prices.size(); i++) {
            maxProfit = max(maxProfit, left[i] + right[i]);
        }
    }

    return maxProfit;
}

int StockBuySell::maxProfitIV(vector<int>& prices, int k) {
    int maxProfit = 0;

    if (prices.size() > 1) {
        int kmin = min(k, (int)prices.size());
        int dp[kmin + 1][prices.size()];

        for (int i = 0; i < prices.size(); i++) {
            dp[0][i] = 0;
        }
        for (int i = 1; i < kmin; i++) {
            dp[i][0] = 0;
        }
        for (int i = 1; i <= kmin; i++) {
            int maxDiff = - prices[0];
            for (int j = 1; j < prices.size(); j++) {
                dp[i][j] = max(dp[i][j - 1], prices[j] + maxDiff);
                maxDiff = max(maxDiff, dp[i - 1][j] - prices[j]);
            }
        }
        maxProfit = dp[kmin][prices.size() - 1];
    }

    return maxProfit;
}