A12425 | Pavel and Triangles
时间限制1s
内存限制256MB
通过 / 提交0/0
题目描述
Pavel has several sticks with lengths equal to powers of two.
He has $a_0$ sticks of length $2^0 = 1$ , $a_1$ sticks of length $2^1 = 2$ , ..., $a_{n-1}$ sticks of length $2^{n-1}$ .
Pavel wants to make the maximum possible number of triangles using these sticks. The triangles should have strictly positive area, each stick can be used in at most one triangle.
It is forbidden to break sticks, and each triangle should consist of exactly three sticks.
Find the maximum possible number of triangles.
He has $a_0$ sticks of length $2^0 = 1$ , $a_1$ sticks of length $2^1 = 2$ , ..., $a_{n-1}$ sticks of length $2^{n-1}$ .
Pavel wants to make the maximum possible number of triangles using these sticks. The triangles should have strictly positive area, each stick can be used in at most one triangle.
It is forbidden to break sticks, and each triangle should consist of exactly three sticks.
Find the maximum possible number of triangles.
输入格式
The first line contains a single integer $n$ ( $1 \leq n \leq 300\,000$ ) — the number of different lengths of sticks.
The second line contains $n$ integers $a_0$ , $a_1$ , ..., $a_{n-1}$ ( $1 \leq a_i \leq 10^9$ ), where $a_i$ is the number of sticks with the length equal to $2^i$ .
The second line contains $n$ integers $a_0$ , $a_1$ , ..., $a_{n-1}$ ( $1 \leq a_i \leq 10^9$ ), where $a_i$ is the number of sticks with the length equal to $2^i$ .
输出格式
Print a single integer — the maximum possible number of non-degenerate triangles that Pavel can make.
输入输出样例
输入 #1
5 1 2 2 2 2
输出 #1
3
输入 #2
3 1 1 1
输出 #2
0
输入 #3
3 3 3 3
输出 #3
3
In the first example, Pavel can, for example, make this set of triangles (the lengths of the sides of the triangles are listed): $(2^0, 2^4, 2^4)$ , $(2^1, 2^3, 2^3)$ , $(2^1, 2^2, 2^2)$ .
In the second example, Pavel cannot make a single triangle.
In the third example, Pavel can, for example, create this set of triangles (the lengths of the sides of the triangles are listed): $(2^0, 2^0, 2^0)$ , $(2^1, 2^1, 2^1)$ , $(2^2, 2^2, 2^2)$ .
In the second example, Pavel cannot make a single triangle.
In the third example, Pavel can, for example, create this set of triangles (the lengths of the sides of the triangles are listed): $(2^0, 2^0, 2^0)$ , $(2^1, 2^1, 2^1)$ , $(2^2, 2^2, 2^2)$ .
C++ 编辑器
输入
输出
可保存默认模板；新题优先使用已保存模板。
当前快捷键仅展示，暂不支持修改。
- 撤销
Ctrl / ⌘ + Z - 重做
Ctrl / ⌘ + Y - 查找
Ctrl / ⌘ + F - 全选
Ctrl / ⌘ + A - 复制
Ctrl / ⌘ + C - 剪切
Ctrl / ⌘ + X - 粘贴
Ctrl / ⌘ + V - 自动排版
工具栏排版按钮 - 草稿保存
编辑时自动保存到本机
历史
提交记录
状态说明时间源码
AI
作答助手
你好，我是作答助手。可以问思路、复杂度、样例含义或代码报错原因；不会直接给出完整 AC 代码。
确定要清空代码吗？
提交通过
评测结果：Accepted