Merge pull request #9 from James-Ren/master

第一周作业#10

Author: GeekUniversity

Week_01/id_10/Leecode-101-10 .py

@@ -0,0 +1,21 @@
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution:
+    def isSymmetric(self, root: TreeNode) -> bool:
+        if not root:
+            return True
+        return self._dfs(root.left, root.right)
+
+    def _dfs(self, node1, node2):
+        if not node1 and node2 or not node2 and node1:
+            return False
+        if node1 and node2 and node1.val != node2.val:
+            return False
+        if not node1 and not node2:
+            return True
+        return self._dfs(node1.left, node2.right) and self._dfs(node2.left, node1.right)

Week_01/id_10/Leecode-1021-10.py

@@ -0,0 +1,14 @@
+class Solution:
+    def removeOuterParentheses(self, S: str) -> str:
+        result=""
+        index=0
+        for c in S:
+            if c=='(':
+                if index!=0:
+                    result+=c
+                index+=1
+            else:
+                index-=1
+                if index!=0:
+                    result+=c
+        return result

Week_01/id_10/Leecode-174-10.py

@@ -0,0 +1,51 @@
+class Solution:
+    # 第一想法  二分法  没有思路
+    # 第二想法  dp  从第一个位置递推到最后，没写出来
+    # 第三想法  暴力法 dfs 遍历所有
+    # 时间复杂度 O(2^N)  空间复杂度 O(1) N为格子总数
+    # 提交超时
+    def calculateMinimumHP(self, dungeon: List[List[int]]) -> int:
+        if len(dungeon) == 0:
+            return 0
+        if len(dungeon[0]) == 0:
+            return 0
+        self.dungeon = dungeon
+        self.minblood = -1
+        self._dfs(0, 0, 0, dungeon[0][0])
+        return self.minblood + 1
+
+    def _dfs(self, i, j, minblood, routeblood):
+        m = len(self.dungeon)
+        n = len(self.dungeon[0])
+        if minblood < 0 - routeblood:
+            minblood = 0 - routeblood
+        if i == m - 1 and j == n - 1:
+            if self.minblood == -1 or self.minblood > minblood:
+                self.minblood = minblood
+        if self.minblood > -1 and self.minblood < minblood:
+            return
+        if i < m - 1:
+            self._dfs(i + 1, j, minblood, routeblood + self.dungeon[i + 1][j])
+        if j < n - 1:
+            self._dfs(i, j + 1, minblood, routeblood + self.dungeon[i][j + 1])
+
+    # 看了解法和评论区  使用逆序dp
+    # 从最后一个位置向前推,的确没想到
+    # 时间复杂度 O(N)  空间复杂度 O(N) N为格子总数
+    def calculateMinimumHP2(self, dungeon: List[List[int]]) -> int:
+        if len(dungeon) == 0:
+            return 0
+        if len(dungeon[0]) == 0:
+            return 0
+        m = len(dungeon)
+        n = len(dungeon[0])
+        dp = [[0 for y in range(n)] for x in range(m)]
+        dp[m - 1][n - 1] = max(1, 1 - dungeon[m - 1][n - 1])
+        for i in range(m - 2, -1, -1):
+            dp[i][n - 1] = max(dp[i + 1][n - 1] - dungeon[i][n - 1], 1)
+        for i in range(n - 2, -1, -1):
+            dp[m - 1][i] = max(dp[m - 1][i + 1] - dungeon[m - 1][i], 1)
+        for i in range(m - 2, -1, -1):
+            for j in range(n - 2, -1, -1):
+                dp[i][j] = min(max(1, dp[i + 1][j] - dungeon[i][j]), max(1, dp[i][j + 1] - dungeon[i][j]))
+        return max(dp[0][0], 1)

Week_01/id_10/Leecode-189-10.py

@@ -0,0 +1,63 @@
+class Solution:
+    def rotate(self, nums: List[int], k: int) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        if len(nums) == 0 or len(nums) == 1:
+            return
+        l = len(nums)
+        if k > l:
+            k = k % l
+
+        endindex = len(nums)
+        startindex = k
+        while k > 0:
+            while startindex + k < endindex:
+                for i in range(k):
+                    tmp = nums[startindex + i]
+                    nums[startindex + i] = nums[i]
+                    nums[i] = tmp
+                startindex = startindex + k
+            if startindex < endindex:
+                leftednum = endindex - startindex
+                for i in range(leftednum):
+                    tmp = nums[startindex + i]
+                    nums[startindex + i] = nums[i]
+                    nums[i] = tmp
+            else:
+                break
+            endindex = k
+            k = k - leftednum
+            startindex = k
+
+    def rotate3(self, nums: List[int], k: int) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        if len(nums) == 0 or len(nums) == 1:
+            return
+        l = len(nums)
+        if k > l:
+            k = k % l
+
+        newarr = nums[len(nums) - k:]
+        for i in range(len(nums) - k - 1, -1, -1):
+            nums[i + k] = nums[i]
+        for i in range(k):
+            nums[i] = newarr[i]
+
+    def rotate2(self, nums: List[int], k: int) -> None:
+        """
+        Do not return anything, modify nums in-place instead.
+        """
+        if len(nums) == 0 or len(nums) == 1:
+            return
+        l = len(nums)
+        if k > l:
+            k = k % l
+
+        for _ in range(k):
+            lastel = nums[l - 1]
+            for i in range(l - 2, -1, -1):
+                nums[i + 1] = nums[i]
+            nums[0] = lastel

Week_01/id_10/Leecode-21-10.py

@@ -0,0 +1,30 @@
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution:
+    def mergeTwoLists(self, l1: ListNode, l2: ListNode) -> ListNode:
+        cur1,cur2=l1,l2
+        head,cur=None,None
+        while cur1 or cur2:
+            prev=cur
+            if cur1 and cur2:
+                if cur1.val>cur2.val:
+                    cur=cur2
+                    cur2=cur2.next
+                else:
+                    cur=cur1
+                    cur1=cur1.next
+            elif cur1:
+                cur=cur1
+                cur1=cur1.next
+            else:
+                cur=cur2
+                cur2=cur2.next
+            if not head:
+                head=cur
+            if prev:
+                prev.next=cur
+        return head

Week_01/id_10/Leecode-236-10.py

@@ -0,0 +1,22 @@
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution:
+    def lowestCommonAncestor(self, root: 'TreeNode', p: 'TreeNode', q: 'TreeNode') -> 'TreeNode':
+        if not root or not p and not q:
+            return None
+        if root==p or root==q:
+            return root
+        leftTree=self.lowestCommonAncestor(root.left,p,q)
+        rightTree=self.lowestCommonAncestor(root.right,p,q)
+        if not leftTree and not rightTree:
+            return None
+        if leftTree and rightTree:
+            return root
+        if leftTree:
+            return leftTree
+        return rightTree

Week_01/id_10/Leecode-24-10.py

@@ -0,0 +1,26 @@
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+# 时间复杂度  O(n)
+# 空间复杂度  O(1)
+class Solution:
+    def swapPairs(self, head: ListNode) -> ListNode:
+        if not head or not head.next:
+            return head
+        last,node1,node2=None,head,head.next
+        head=node2
+        while node2:
+            nextnode=node2.next
+            node2.next=node1
+            if last:
+                last.next=node2
+            node1.next=nextnode
+            if not nextnode:
+                break
+            last=node1
+            node1=nextnode
+            node2=nextnode.next
+        return head

Week_01/id_10/Leecode-257-10.go

@@ -0,0 +1,39 @@
+import "strconv"
+
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+var allroutes []string
+
+func binaryTreePaths(root *TreeNode) []string {
+	if root == nil {
+		return []string{}
+	}
+	allroutes = make([]string, 0)
+	dfs("", root)
+	return allroutes
+}
+
+func dfs(str string, root *TreeNode) {
+	curroute := ""
+	if str == "" {
+		curroute = strconv.Itoa(root.Val)
+	} else {
+		curroute = str + "->" + strconv.Itoa(root.Val)
+	}
+	if root.Left == nil && root.Right == nil {
+		allroutes = append(allroutes, curroute)
+		return
+	}
+	if root.Left != nil {
+		dfs(curroute, root.Left)
+	}
+	if root.Right != nil {
+		dfs(curroute, root.Right)
+	}
+}

Week_01/id_10/Leecode-42-10.go

@@ -0,0 +1,41 @@
+func trap(height []int) int {
+	totals := 0
+	startpos := 0
+	for i := 1; i < len(height); i++ {
+		curh := height[i]
+		if curh >= height[startpos] {
+			minh := height[startpos]
+			curw := i - startpos - 1
+			if curw == 0 {
+				startpos = i
+				continue
+			}
+			rangenums := minh * curw
+			for j := startpos + 1; j < i; j++ {
+				rangenums -= height[j]
+			}
+			totals += rangenums
+			startpos = i
+		}
+	}
+	biggestpos := startpos
+	startpos = len(height) - 1
+	for i := len(height) - 2; i >= biggestpos; i-- {
+		curh := height[i]
+		if curh >= height[startpos] {
+			minh := height[startpos]
+			curw := startpos - i - 1
+			if curw == 0 {
+				startpos = i
+				continue
+			}
+			rangenums := minh * curw
+			for j := i + 1; j < startpos; j++ {
+				rangenums -= height[j]
+			}
+			totals += rangenums
+			startpos = i
+		}
+	}
+	return totals
+}

Week_01/id_10/Leecode-49-10.py

@@ -0,0 +1,9 @@
+class Solution:
+    def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
+        strmap={}
+        for s in strs:
+            ss=''.join(sorted(s))
+            strarr=strmap.get(ss,[])
+            strarr.append(s)
+            strmap[ss]=strarr
+        return list(strmap.values())

Week_01/id_10/Leecode-50-10.py

@@ -0,0 +1,24 @@
+
+# 看了别人的代码仿照写的
+# 时间复杂度  O(logN)
+# 利用位运算做除2和奇偶判断
+# 空间复杂度  O(1)
+class Solution:
+    def myPow(self, x: float, n: int) -> float:
+        isNegitive=False
+        if n==0:
+            return 1.0
+        if n==1:
+            return x
+        if n<0:
+            isNegitive=True
+            n=0-n
+        res,p=1,x
+        while n!=0:
+            if n&1==1:
+                res*=p
+            p*=p
+            n>>=1
+        if isNegitive:
+            res=1.0/res
+        return res

Week_01/id_10/Leecode-84-10.py

@@ -0,0 +1,31 @@
+class Solution:
+    def largestRectangleArea(self, heights: List[int]) -> int:
+        if len(heights)==0:
+            return 0
+        stack=collections.deque()
+        maxarea=0
+        for i in range(len(heights)):
+            h=heights[i]
+            l=len(stack)
+            if l>0:
+                startindex=stack[len(stack)-1]
+            while l>0 and heights[startindex]>h:
+                popindex=stack.pop()
+                l-=1
+                startindex=-1
+                if l>0:
+                    startindex=stack[l-1]
+                area=(i-startindex-1)*heights[popindex]
+                if maxarea<area:
+                    maxarea=area
+            stack.append(i)
+        lastindex=stack[len(stack)-1]
+        for i in range(len(stack)-1,-1,-1):
+            if i>0:
+                startindex=stack[i-1]
+            else:
+                startindex=-1
+            area=heights[stack[i]]*(lastindex-startindex)
+            if maxarea<area:
+                maxarea=area
+        return maxarea