创建特定大小的零向量 [英] Creating a vector of zeros for a specific size

问题描述

我想用在运行时确定的特定大小初始化一个零向量.

I'd like to initialize a vector of zeros with a specific size that is determined at runtime.

在 C 中，它会是这样的:

In C, it would be like:

int main(void)
{
    uint size = get_uchar();
    int A[size][size];
    memset(A, 0, size*size*sizeof(int));
}

这是我尝试用 Rust 编写的辅助函数，但我认为切片语法 0..size 冒犯了编译器.此外，它看起来比 C 版本更冗长.有没有更惯用的方法来做到这一点?

Here's the helper function that I tried writing in Rust, but I think the slicing syntax 0..size is offending the compiler. Besides, it looks more verbose than the C version. Is there a more idiomatic way to do this?

fn zeros(size: u32) -> Vec<i32> {
    let mut zero_vec: Vec<i32> = Vec::with_capacity(size);
    for i in 0..size {
        zero_vec.push(0);
    }
    return zero_vec;
}

我发誓旧文档曾经解释过 from_elem() 方法 here 并且没有 [0 的任何排列；大小] 符号似乎有效

I swear that the old docs used to explain a from_elem() method here and none of the permutations of the [0 ; size] notation seem to work

我想最终将其粘贴到子字符串搜索算法中:

I'd like to stick this into a substring search algorithm ultimately:

pub fn kmp(text: &str, pattern: &str) -> i64 {
    let mut shifts = zeros(pattern.len()+1);
}

推荐答案

要初始化给定长度的零向量(或任何其他常量值)，您可以使用 vec! 宏:

To initialize a vector of zeros (or any other constant value) of a given length, you can use the vec! macro:

let len = 10;
let zero_vec = vec![0; len];

也就是说，经过几个语法修复后，您的函数对我有用:

That said, your function worked for me after just a couple syntax fixes:

fn zeros(size: u32) -> Vec<i32> {
    let mut zero_vec: Vec<i32> = Vec::with_capacity(size as usize);
    for i in 0..size {
        zero_vec.push(0);
    }
    return zero_vec;
}

uint 在 Rust 1.0 中不再存在，size 需要转换为 usize，并且需要匹配的向量类型(将 let mut zero_vec: Vec 更改为 let mut zero_vec: Vec.

uint no longer exists in Rust 1.0, size needed to be cast as usize, and the types for the vectors needed to match (changed let mut zero_vec: Vec<i64> to let mut zero_vec: Vec<i32>.

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