Commit 391a04b

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Merge pull request youngyangyang04#623 from DoubleYellowIce/master

添加买卖股票的最佳时机 IV java版本一维空间优化代码

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Original file line number	Diff line number	Diff line change
`@@ -196,7 +196,7 @@ class Solution {`
`196`	`196`	`}`
`197`	`197`	`}`
`198`	`198`
`199`		`-// 版本二: 空间优化`
	`199`	`+// 版本二: 二维 dp数组`
`200`	`200`	`class Solution {`
`201`	`201`	`public int maxProfit(int k, int[] prices) {`
`202`	`202`	`if (prices.length == 0) return 0;`
`@@ -220,6 +220,25 @@ class Solution {`
`220`	`220`	`return dp[len - 1][k*2];`
`221`	`221`	`}`
`222`	`222`	`}`
	`223`	`+`
	`224`	`+//版本三:一维 dp数组`
	`225`	`+class Solution {`
	`226`	`+ public int maxProfit(int k, int[] prices) {`
	`227`	`+ //在版本二的基础上,由于我们只关心前一天的股票买入情况,所以只存储前一天的股票买入情况`
	`228`	`+ if(prices.length==0)return 0;`
	`229`	`+ int[] dp=new int[2*k+1];`
	`230`	`+ for (int i = 1; i <2*k ; i+=2) {`
	`231`	`+ dp[i]=-prices[0];`
	`232`	`+ }`
	`233`	`+ for (int i = 0; i <prices.length ; i++) {`
	`234`	`+ for (int j = 1; j <2*k ; j+=2) {`
	`235`	`+ dp[j]=Math.max(dp[j],dp[j-1]-prices[i]);`
	`236`	`+ dp[j+1]=Math.max(dp[j+1],dp[j]+prices[i]);`
	`237`	`+ }`
	`238`	`+ }`
	`239`	`+ return dp[2*k];`
	`240`	`+ }`
	`241`	`+}`
`223`	`242`	```
`224`	`243`
`225`	`244`

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