[pull] master from youngyangyang04:master #305

Original file line number	Diff line number	Diff line change
Expand Up		@@ -413,7 +413,52 @@ function maxProfit(prices: number[]): number {
		};
		```

	Rust:

	> 版本一

	```rust
	impl Solution {
	pub fn max_profit(prices: Vec<i32>) -> i32 {
	/*
	* 定义 5 种状态:
	* 0: 没有操作, 1: 第一次买入, 2: 第一次卖出, 3: 第二次买入, 4: 第二次卖出
	*/
	let mut dp = vec![vec![0; 5]; prices.len()];
	dp[0][1] = -prices[0];
	dp[0][3] = -prices[0];

	for (i, &p) in prices.iter().enumerate().skip(1) {
	// 不操作
	// dp[i][0] = dp[i - 1][0];
	dp[i][1] = dp[i - 1][1].max(-p);
	dp[i][2] = dp[i - 1][2].max(dp[i - 1][1] + p);
	dp[i][3] = dp[i - 1][3].max(dp[i - 1][2] - p);
	dp[i][4] = dp[i - 1][4].max(dp[i - 1][3] + p);
	}

	dp[prices.len() - 1][4]
	}
	}
	```

	> 版本二(绕)

	```rust
	impl Solution {
	pub fn max_profit(prices: Vec<i32>) -> i32 {
	let (mut one_buy, mut one_sale, mut two_buy, mut two_sale) = (-prices[0], 0, -prices[0], 0);

	for p in prices {
	one_buy = one_buy.max(-p);
	one_sale = one_sale.max(p + one_buy);
	two_buy = two_buy.max(one_sale - p);
	two_sale = two_sale.max(two_buy + p);
	}
	two_sale
	}
	}
	```


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49 changes: 49 additions & 0 deletions problems/0188.买卖股票的最佳时机IV.md

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -474,6 +474,55 @@ function maxProfit(k: number, prices: number[]): number {
		};
		```

	Rust:

	```rust
	impl Solution {
	pub fn max_profit(k: i32, prices: Vec<i32>) -> i32 {
	let mut dp = vec![vec![0; 2 * k as usize + 1]; prices.len()];

	for v in dp[0].iter_mut().skip(1).step_by(2) {
	*v = -prices[0];
	}

	for (i, &p) in prices.iter().enumerate().skip(1) {
	for j in (0..2 * k as usize - 1).step_by(2) {
	dp[i][j + 1] = dp[i - 1][j + 1].max(dp[i - 1][j] - p);
	dp[i][j + 2] = dp[i - 1][j + 2].max(dp[i - 1][j + 1] + p);
	}
	}

	dp[prices.len() - 1][2 * k as usize]
	}
	}
	```

	空间优化:

	```rust
	impl Solution {
	pub fn max_profit(k: i32, prices: Vec<i32>) -> i32 {
	let mut dp = vec![0; 2 * k as usize + 1];
	for v in dp.iter_mut().skip(1).step_by(2) {
	*v = -prices[0];
	}

	for p in prices {
	for i in 1..=2 * k as usize {
	if i % 2 == 1 {
	// 买入
	dp[i] = dp[i].max(dp[i - 1] - p);
	continue;
	}
	// 卖出
	dp[i] = dp[i].max(dp[i - 1] + p);
	}
	}

	dp[2 * k as usize]
	}
	}
	```


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