Best Time to Buy and Sell Stock IV LeetCode solution in C++

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class Solution {
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 public:
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  int solve(int ind, int buy, int k, vector<int> &prices, vector<vector<vector<int>>> &dp) {
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    if (k == 0 || ind == prices.size()) return 0;
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    if (dp[ind][buy][k] != -1) return dp[ind][buy][k];
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    if (buy) {
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      return dp[ind][buy][k] = max(-prices[ind] + solve(ind + 1, 0, k, prices, dp),
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                                   solve(ind + 1, 1, k, prices, dp));
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    }
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    return dp[ind][buy][k] = max(prices[ind] + solve(ind + 1, 1, k - 1, prices, dp),
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                                 solve(ind + 1, 0, k, prices, dp));
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  }
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  int maxProfit(int k, vector<int> &prices) {
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    vector<vector<vector<int>>> dp(prices.size(), vector<vector<int>>(2, vector<int>(k + 1, -1)));
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    return solve(0, 1, k, prices, dp);
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  }
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};