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🐱(array): 119. 杨辉三角 II

补充递归

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docs/data-structure/array
- README.md

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`‎docs/data-structure/array/README.md‎`

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Original file line number	Diff line number	Diff line change
`@@ -1087,6 +1087,27 @@ class Solution(object):`
`1087`	`1087`	`return res`
`1088`	`1088`	```
`1089`	`1089`
	`1090`	`+优化:`
	`1091`	`+`
	`1092`	+```go
	`1093`	`+func generate(numRows int) [][]int {`
	`1094`	`+ var res [][]int = make([][]int, numRows)`
	`1095`	`+`
	`1096`	`+ for i := 0; i < numRows; i++ {`
	`1097`	`+ res[i] = make([]int, i + 1)`
	`1098`	`+ for j := 0; j < i + 1; j++ {`
	`1099`	`+ if j == 0 \|\| j == i {`
	`1100`	`+ res[i][j] = 1`
	`1101`	`+ } else {`
	`1102`	`+ res[i][j] = res[i - 1][j - 1] + res[i - 1][j]`
	`1103`	`+ }`
	`1104`	`+ }`
	`1105`	`+ }`
	`1106`	`+`
	`1107`	`+ return res`
	`1108`	`+}`
	`1109`	+```
	`1110`	`+`
`1090`	`1111`
`1091`	`1112`	`## 119. 杨辉三角 II`
`1092`	`1113`
`@@ -1124,6 +1145,32 @@ class Solution(object):`
`1124`	`1145`	`return cur`
`1125`	`1146`	```
`1126`	`1147`
	`1148`	`+### 解二:递归`
	`1149`	`+`
	`1150`	+```python
	`1151`	`+class Solution:`
	`1152`	`+ def generate(self, numRows: int) -> List[List[int]]:`
	`1153`	`+ ans = []`
	`1154`	`+ # 递归:输入上一行,返回下一行`
	`1155`	`+ def helper(pre):`
	`1156`	`+ length = len(pre)`
	`1157`	`+ if length == numRows:`
	`1158`	`+ return`
	`1159`	`+ if length == 0:`
	`1160`	`+ nxt = [1]`
	`1161`	`+ elif length == 1:`
	`1162`	`+ nxt = [1, 1]`
	`1163`	`+ else:`
	`1164`	`+ nxt = [1]`
	`1165`	`+ for i in range(length - 1):`
	`1166`	`+ nxt.append(pre[i] + pre[i + 1])`
	`1167`	`+ nxt.append(1)`
	`1168`	`+ ans.append(nxt)`
	`1169`	`+ helper(nxt)`
	`1170`	`+`
	`1171`	`+ helper([])`
	`1172`	`+ return ans`
	`1173`	+```
`1127`	`1174`
`1128`	`1175`	`## 121. 买卖股票的最佳时机`
`1129`	`1176`

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`‎docs/data-structure/array/README.md‎`

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