算法刷题Day 41 整数拆分+不同的二叉搜索树

Day 41 动态规划

343. 整数拆分

class Solution {
public:
    int integerBreak(int n) {
        if (n == 2) return 1;
        if (n == 3) return 2;
        if (n == 4) return 4;

        int a = 2, b = 3, c = 4;
        for (int i = 5; i <= n; i++)
        {
            int tmp = max(b * 2, a * 3);
            a = b;
            b = c;
            c = tmp;
        }

        return c;
    }
};

96. 不同的二叉搜索树

这道题没回忆起来，稍微参考了一下答案

class Solution {
public:
    int numTrees(int n) {
        vector<int> table(n + 1, 0);
        table[0] = 1;

        for (int i = 1; i < table.size(); i++)
        {
            int sum = 0;
            for (int j = 1; j <= i; j++)
            {
                sum += table[j - 1] * table[i - j];
            }

            table[i] = sum;
        }

        return table[n];
    }
};