algorithm/Algorithm/cpp/0343.IntegerBreak/integerBreak.cpp at master · wuvei/algorithm · GitHub

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// math
class Solution {
public:
    int integerBreak(int n) {
        if (n <= 3) {
            return n - 1;
        }
        int quotient = n / 3;
        int remainder = n % 3;
        if (remainder == 0) {
            return (int)pow(3, quotient);
        } else if (remainder == 1) {
            return (int)pow(3, quotient - 1) * 4;
        } else {
            return (int)pow(3, quotient) * 2;
        }
    }
};

// dp
class Solution {
public:
    int integerBreak(int n) {
        if (n < 4) return n - 1;
        vector<int> dp(n + 1, 0);
        dp[2] = 1;
        dp[3] = 2;
        for (int i = 4; i <= n; i++) {
            for (int j = 1; j < i; j++) {
                dp[i] = std::max({dp[i - j] * j, (i - j) * j, dp[i]});
            }
        }
        return dp[n];
    }
};