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# 27. 移除元素 | ||
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## 题目描述 | ||
给你一个数组 nums 和一个值 val,你需要 原地 移除所有数值等于 val 的元素,并返回移除后数组的新长度。 | ||
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不要使用额外的数组空间,你必须仅使用 O(1) 额外空间并 原地 修改输入数组。 | ||
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元素的顺序可以改变。你不需要考虑数组中超出新长度后面的元素。 | ||
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0 <= nums.length <= 100 | ||
0 <= nums[i] <= 50 | ||
0 <= val <= 100 | ||
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## 解题思路 | ||
线性算法,找到一个要移除的元素就和最后一个交换 | ||
```rust | ||
# struct Solution {} | ||
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impl Solution { | ||
pub fn remove_element(nums: &mut Vec<i32>, val: i32) -> i32 { | ||
let n = nums.len(); | ||
if n == 0 { return 0 } | ||
// [i,j) 表示还需要处理的区间,在这个区间之外的都是无需处理的 | ||
let mut i = 0; | ||
let mut j = n; | ||
while i < j { | ||
if nums[i] == val { | ||
j -= 1; | ||
nums[i] = nums[j]; | ||
} else { | ||
i += 1; | ||
} | ||
} | ||
j as i32 | ||
} | ||
} | ||
``` | ||
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## 学习感想 | ||
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一开始想的时候其实有不变量的思想在里面 | ||
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写一下 双指针的版本 | ||
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```rust | ||
# struct Solution {} | ||
impl Solution { | ||
pub fn remove_element(nums: &mut Vec<i32>, val: i32) -> i32 { | ||
let mut a = 0; | ||
let mut b = 0; | ||
let n = nums.len(); | ||
while b < n { | ||
if nums[b] == val { b += 1 } | ||
else { | ||
nums[a] = nums[b]; | ||
a += 1; | ||
b += 1; | ||
} | ||
} | ||
a as i32 | ||
} | ||
} | ||
``` |
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# 第一章 数组part02 | ||
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977.有序数组的平方 y,209.长度最小的子数组 ,59.螺旋矩阵II ,总结 | ||
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建议大家先独立做题,然后看视频讲解,然后看文章讲解,然后在重新做一遍题,把题目AC,最后整理成今日当天的博客 | ||
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拓展题目可以先不做 | ||
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详细布置 | ||
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## 977.有序数组的平方 | ||
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题目建议: 本题关键在于理解双指针思想 | ||
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题目链接:https://leetcode.cn/problems/squares-of-a-sorted-array/ | ||
文章讲解:https://programmercarl.com/0977.%E6%9C%89%E5%BA%8F%E6%95%B0%E7%BB%84%E7%9A%84%E5%B9%B3%E6%96%B9.html | ||
视频讲解: https://www.bilibili.com/video/BV1QB4y1D7ep | ||
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## 209.长度最小的子数组 | ||
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题目建议: 本题关键在于理解滑动窗口,这个滑动窗口看文字讲解 还挺难理解的,建议大家先看视频讲解。 拓展题目可以先不做。 | ||
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题目链接:https://leetcode.cn/problems/minimum-size-subarray-sum/ | ||
文章讲解:https://programmercarl.com/0209.%E9%95%BF%E5%BA%A6%E6%9C%80%E5%B0%8F%E7%9A%84%E5%AD%90%E6%95%B0%E7%BB%84.html | ||
视频讲解:https://www.bilibili.com/video/BV1tZ4y1q7XE | ||
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## 59.螺旋矩阵II | ||
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题目建议: 本题关键还是在转圈的逻辑,在二分搜索中提到的区间定义,在这里又用上了。 | ||
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题目链接:https://leetcode.cn/problems/spiral-matrix-ii/ | ||
文章讲解:https://programmercarl.com/0059.%E8%9E%BA%E6%97%8B%E7%9F%A9%E9%98%B5II.html | ||
视频讲解:https://www.bilibili.com/video/BV1SL4y1N7mV/ | ||
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总结 | ||
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题目建议:希望大家 也做一个自己 对数组专题的总结 | ||
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文章链接:https://programmercarl.com/%E6%95%B0%E7%BB%84%E6%80%BB%E7%BB%93%E7%AF%87.html | ||
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# 27. 移除元素 | ||
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# | ||
## 题目描述 | ||
给你一个数组 nums 和一个值 val,你需要 原地 移除所有数值等于 val 的元素,并返回移除后数组的新长度。 | ||
|
||
不要使用额外的数组空间,你必须仅使用 O(1) 额外空间并 原地 修改输入数组。 | ||
|
||
元素的顺序可以改变。你不需要考虑数组中超出新长度后面的元素。 | ||
|
||
|
||
0 <= nums.length <= 100 | ||
0 <= nums[i] <= 50 | ||
0 <= val <= 100 | ||
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||
## 解题思路 | ||
线性算法,找到一个要移除的元素就和最后一个交换 | ||
```rust | ||
# struct Solution {} | ||
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||
impl Solution { | ||
pub fn remove_element(nums: &mut Vec<i32>, val: i32) -> i32 { | ||
let n = nums.len(); | ||
if n == 0 { return 0 } | ||
// [i,j) 表示还需要处理的区间,在这个区间之外的都是无需处理的 | ||
let mut i = 0; | ||
let mut j = n; | ||
while i < j { | ||
if nums[i] == val { | ||
j -= 1; | ||
nums[i] = nums[j]; | ||
} else { | ||
i += 1; | ||
} | ||
} | ||
j as i32 | ||
} | ||
} | ||
``` | ||
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## 学习感想 | ||
|
||
一开始想的时候其实有不变量的思想在里面 | ||
|
||
写一下 双指针的版本 | ||
|
||
|
||
```rust | ||
# struct Solution {} | ||
impl Solution { | ||
pub fn remove_element(nums: &mut Vec<i32>, val: i32) -> i32 { | ||
let mut a = 0; | ||
let mut b = 0; | ||
let n = nums.len(); | ||
while b < n { | ||
if nums[b] == val { b += 1 } | ||
else { | ||
nums[a] = nums[b]; | ||
a += 1; | ||
b += 1; | ||
} | ||
} | ||
a as i32 | ||
} | ||
} | ||
``` | ||
## 学习感想 |