|
| 1 | +--- |
| 2 | +comments: true |
| 3 | +difficulty: 中等 |
| 4 | +edit_url: https://github.com/doocs/leetcode/edit/main/solution/3700-3799/3792.Sum%20of%20Increasing%20Product%20Blocks/README.md |
| 5 | +--- |
| 6 | + |
| 7 | +<!-- problem:start --> |
| 8 | + |
| 9 | +# [3792. 递增乘积块之和 🔒](https://leetcode.cn/problems/sum-of-increasing-product-blocks) |
| 10 | + |
| 11 | +[English Version](/solution/3700-3799/3792.Sum%20of%20Increasing%20Product%20Blocks/README_EN.md) |
| 12 | + |
| 13 | +## 题目描述 |
| 14 | + |
| 15 | +<!-- description:start --> |
| 16 | + |
| 17 | +<p>给定一个整数 <code>n</code>。</p> |
| 18 | + |
| 19 | +<p>一个序列的形成如下:</p> |
| 20 | + |
| 21 | +<ul> |
| 22 | + <li>第 <code>1</code> 块包含 <code>1</code>。</li> |
| 23 | + <li>第 <code>2</code> 块包含 <code>2 * 3</code>。</li> |
| 24 | + <li>第 <code>i</code> 块是之后 <code>i</code> 个连续整数的乘积。</li> |
| 25 | +</ul> |
| 26 | + |
| 27 | +<p>令 <code>F(n)</code> 为前 <code>n</code> 块之和。</p> |
| 28 | + |
| 29 | +<p>返回一个整数表示 <code>F(n)</code> <strong>模上</strong> <code>10<sup>9</sup> + 7</code>。</p> |
| 30 | + |
| 31 | +<p> </p> |
| 32 | + |
| 33 | +<p><strong class="example">示例 1:</strong></p> |
| 34 | + |
| 35 | +<div class="example-block"> |
| 36 | +<p><span class="example-io"><b>输入:</b>n = 3</span></p> |
| 37 | + |
| 38 | +<p><span class="example-io"><b>输出:</b>127</span></p> |
| 39 | + |
| 40 | +<p><strong>解释:</strong></p> |
| 41 | + |
| 42 | +<ul> |
| 43 | + <li>块 1:<code>1</code></li> |
| 44 | + <li>块 2:<code>2 * 3 = 6</code></li> |
| 45 | + <li>块 3:<code>4 * 5 * 6 = 120</code></li> |
| 46 | +</ul> |
| 47 | + |
| 48 | +<p><code>F(3) = 1 + 6 + 120 = 127</code></p> |
| 49 | +</div> |
| 50 | + |
| 51 | +<p><strong class="example">示例 2:</strong></p> |
| 52 | + |
| 53 | +<div class="example-block"> |
| 54 | +<p><span class="example-io"><b>输入:</b>n = 7</span></p> |
| 55 | + |
| 56 | +<p><span class="example-io"><b>输出:</b>6997165</span></p> |
| 57 | + |
| 58 | +<p><strong>解释:</strong></p> |
| 59 | + |
| 60 | +<ul> |
| 61 | + <li>块 1:<code>1</code></li> |
| 62 | + <li>块 2:<code>2 * 3 = 6</code></li> |
| 63 | + <li>块 3:<code>4 * 5 * 6 = 120</code></li> |
| 64 | + <li>块 4:<code>7 * 8 * 9 * 10 = 5040</code></li> |
| 65 | + <li>块 5:<code>11 * 12 * 13 * 14 * 15 = 360360</code></li> |
| 66 | + <li>块 6:<code>16 * 17 * 18 * 19 * 20 * 21 = 39070080</code></li> |
| 67 | + <li>块 7:<code>22 * 23 * 24 * 25 * 26 * 27 * 28 = 5967561600</code></li> |
| 68 | +</ul> |
| 69 | + |
| 70 | +<p><code>F(7) = 6006997207 % (10<sup>9</sup> + 7) = 6997165</code></p> |
| 71 | +</div> |
| 72 | + |
| 73 | +<p> </p> |
| 74 | + |
| 75 | +<p><strong>提示:</strong></p> |
| 76 | + |
| 77 | +<ul> |
| 78 | + <li><code>1 <= n <= 1000</code></li> |
| 79 | +</ul> |
| 80 | + |
| 81 | +<!-- description:end --> |
| 82 | + |
| 83 | +## 解法 |
| 84 | + |
| 85 | +<!-- solution:start --> |
| 86 | + |
| 87 | +### 方法一:模拟 |
| 88 | + |
| 89 | +我们可以直接模拟每一块的乘积并累加到答案中。需要注意的是,由于乘积可能会非常大,我们需要在每一步计算时对结果取模。 |
| 90 | + |
| 91 | +时间复杂度 $O(n^2)$,空间复杂度 $O(1)$。 |
| 92 | + |
| 93 | +<!-- tabs:start --> |
| 94 | + |
| 95 | +#### Python3 |
| 96 | + |
| 97 | +```python |
| 98 | +class Solution: |
| 99 | + def sumOfBlocks(self, n: int) -> int: |
| 100 | + ans = 0 |
| 101 | + mod = 10**9 + 7 |
| 102 | + k = 1 |
| 103 | + for i in range(1, n + 1): |
| 104 | + x = 1 |
| 105 | + for j in range(k, k + i): |
| 106 | + x = (x * j) % mod |
| 107 | + ans = (ans + x) % mod |
| 108 | + k += i |
| 109 | + return ans |
| 110 | +``` |
| 111 | + |
| 112 | +#### Java |
| 113 | + |
| 114 | +```java |
| 115 | +class Solution { |
| 116 | + public int sumOfBlocks(int n) { |
| 117 | + final int mod = (int) 1e9 + 7; |
| 118 | + long ans = 0; |
| 119 | + int k = 1; |
| 120 | + for (int i = 1; i <= n; ++i) { |
| 121 | + long x = 1; |
| 122 | + for (int j = k; j < k + i; ++j) { |
| 123 | + x = x * j % mod; |
| 124 | + } |
| 125 | + ans = (ans + x) % mod; |
| 126 | + k += i; |
| 127 | + } |
| 128 | + return (int) ans; |
| 129 | + } |
| 130 | +} |
| 131 | +``` |
| 132 | + |
| 133 | +#### C++ |
| 134 | + |
| 135 | +```cpp |
| 136 | +class Solution { |
| 137 | +public: |
| 138 | + int sumOfBlocks(int n) { |
| 139 | + const int mod = 1e9 + 7; |
| 140 | + long long ans = 0; |
| 141 | + int k = 1; |
| 142 | + for (int i = 1; i <= n; ++i) { |
| 143 | + long long x = 1; |
| 144 | + for (int j = k; j < k + i; ++j) { |
| 145 | + x = x * j % mod; |
| 146 | + } |
| 147 | + ans = (ans + x) % mod; |
| 148 | + k += i; |
| 149 | + } |
| 150 | + return ans; |
| 151 | + } |
| 152 | +}; |
| 153 | +``` |
| 154 | +
|
| 155 | +#### Go |
| 156 | +
|
| 157 | +```go |
| 158 | +func sumOfBlocks(n int) (ans int) { |
| 159 | + const mod int = 1e9 + 7 |
| 160 | + k := 1 |
| 161 | + for i := 1; i <= n; i++ { |
| 162 | + x := 1 |
| 163 | + for j := k; j < k+i; j++ { |
| 164 | + x = x * j % mod |
| 165 | + } |
| 166 | + ans = (ans + x) % mod |
| 167 | + k += i |
| 168 | + } |
| 169 | + return |
| 170 | +} |
| 171 | +``` |
| 172 | + |
| 173 | +#### TypeScript |
| 174 | + |
| 175 | +```ts |
| 176 | +function sumOfBlocks(n: number): number { |
| 177 | + const mod = 1000000007; |
| 178 | + let k = 1; |
| 179 | + let ans = 0; |
| 180 | + for (let i = 1; i <= n; i++) { |
| 181 | + let x = 1; |
| 182 | + for (let j = k; j < k + i; j++) { |
| 183 | + x = (x * j) % mod; |
| 184 | + } |
| 185 | + ans = (ans + x) % mod; |
| 186 | + k += i; |
| 187 | + } |
| 188 | + return ans; |
| 189 | +} |
| 190 | +``` |
| 191 | + |
| 192 | +<!-- tabs:end --> |
| 193 | + |
| 194 | +<!-- solution:end --> |
| 195 | + |
| 196 | +<!-- problem:end --> |
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