commit 119/121

Author: Forge Yao

119/119-getRow.go

@@ -0,0 +1,39 @@
+// https://leetcode-cn.com/problems/pascals-triangle-ii/
+package main
+
+import "fmt"
+
+func getRow(rowIndex int) []int {
+	// 构造完整的杨辉三角形. 二维数组
+	/*num := make([][]int, rowIndex+1)
+	for i := 0; i <= rowIndex; i++ {
+		num[i] = make([]int, i+1)
+		num[i][0] = 1
+		num[i][i] = 1
+		for j := 1; j < i; j++ {
+			num[i][j] = num[i-1][j-1] + num[i-1][j]
+		}
+	}
+	return num[rowIndex]*/
+
+	// 节省空间版。一维数组
+	num := make([]int, rowIndex+1)
+	num[0] = 1
+	for i := 1; i <= rowIndex; i++ {
+		num[i] = 1
+		pre := num[0]
+		for j := 1; j < i; j++ {
+			cur := num[j]
+			num[j] = pre + cur
+			pre = cur
+		}
+	}
+	return num
+}
+
+func main() {
+	n := []int{3, 4, 5}
+	for i := 0; i < len(n); i++ {
+		fmt.Println("ret:", getRow(n[i]))
+	}
+}

121/121-maxProfit.go

@@ -0,0 +1,55 @@
+// https://leetcode-cn.com/problems/best-time-to-buy-and-sell-stock/
+package main
+
+import "fmt"
+
+func maxProfit2(prices []int) int {
+	length := len(prices)
+	min, max, diff := 0, 0, 0
+	for i := 1; i < length; {
+		if prices[min] >= prices[i] {
+			min = i
+			i++
+			continue
+		} else {
+			max = i
+			for j := i + 1; j < length; j++ {
+				if prices[j] > prices[max] {
+					max = j
+				}
+			}
+			for j := i + 1; j < max; j++ {
+				if prices[min] > prices[j] {
+					min = j
+				}
+			}
+		}
+		if max > min && prices[max]-prices[min] > diff {
+			diff = prices[max] - prices[min]
+		}
+		i = max + 2
+		min = max + 1
+		max = max + 1
+	}
+	return diff
+}
+
+func maxProfit(prices []int) int {
+	min, maxDiff := prices[0], 0
+	for i := 1; i < len(prices); i++ {
+		if prices[i]-min > maxDiff {
+			maxDiff = prices[i] - min
+		}
+		if prices[i] < min {
+			min = prices[i]
+		}
+	}
+	return maxDiff
+}
+
+func main() {
+	n := [][]int{{7, 1, 5, 3, 6, 4}, {7, 6, 4, 3, 1}, {1, 2, 3, 4, 5}, {4, 5, 6, 7, 1, 5}, {4, 5, 2, 7, 8}}
+	for i := 0; i < len(n); i++ {
+		fmt.Println("ret:", maxProfit(n[i]))
+	}
+}

README.md

@@ -35,6 +35,8 @@ LeetCode
 |111|[二叉树的最小深度](https://leetcode-cn.com/problems/minimum-depth-of-binary-tree/)|[Go](./111/111-minDepth.go)|简单|二叉树|
 |112|[路径总和](https://leetcode-cn.com/problems/path-sum/)|[Go](./112/112-hasPathSum.go)|简单|二叉树|
 |118|[杨辉三角](https://leetcode-cn.com/problems/pascals-triangle/)|[Go](./118/118-generate.go)|简单||
+|119|[杨辉三角 II](https://leetcode-cn.com/problems/pascals-triangle-ii/)|[Go](./119/119-getRow.go)|简单||
+|121|[买卖股票的最佳时机](https://leetcode-cn.com/problems/best-time-to-buy-and-sell-stock/)|[Go](./121/121-maxProfit.go)|简单||
 |125|[验证回文串](https://leetcode-cn.com/problems/valid-palindrome/)|[Go](./125-isPalindrome/125-isPalindrome.go)|简单||
 |131|[分割回文串](https://leetcode-cn.com/problems/palindrome-partitioning/) | [Go](./131-partition/131-partition.go)|中等|递归, 动态规划|
 |141|[环形链表](https://leetcode-cn.com/problems/linked-list-cycle/)|[Go](./141-hasCycle/141-hasCycle.go)|简单|双指针|