2020-09-20

Author: JiayangWu

0012.整数转罗马数字/0012-整数转罗马数字.py

@@ -4,13 +4,16 @@ def intToRoman(self, num):
         :type num: int
         :rtype: str
         """
-        digit = [1000,900,500,400,100,90,50,40,10,9,5,4,1]
-        mapping = {1000:"M", 900:"CM", 500:"D",400:"CD", 100:"C", 90: "XC", 50:"L",40: "XL", 10:"X", 9:"IX", 5:"V", 4:"IV", 1:"I"}
+        l = [(1000, "M"), (900, "CM"), (500, "D"), (400, "CD"), \
+             (100, "C"), (90, "XC"), (50, "L"), (40, "XL"), (10, "X"), \
+             (9, "IX"), (5, "V"), (4, "IV"), (1, "I")][::-1]
         res = ""
-        for i in digit:
-            res += (num / i) * mapping[i]
-            num -= i * (num / i)
-            if num == 0:
-                break
-        return res
-
+        while num:
+            for value, ch in l[::-1]:
+                if num >= value:
+                    res += ch 
+                    num -= value 
+                    break
+                else:
+                    l.pop()
+        return res

0013.罗马数字转整数/0013-罗马数字转整数.py

@@ -4,21 +4,15 @@ def romanToInt(self, s):
         :type s: str
         :rtype: int
         """
-        dic = {"I": 1, "V":5, "X": 10, "L":50, "C":100, "D": 500, "M": 1000}
-        stack = []
+        dic = {"I":1, "V": 5, "X":10, "L":50, "C":100, "D":500, "M":1000}
         res = 0
-        for inx, item in enumerate(s):
-            res += dic[item]
-            # print res
-            # s.append(item)
-            if item == "V" or item == "X":
-                if stack and stack[-1] == "I":
-                    res -= 2
-            elif item == "L" or item == "C":
-                if stack and stack[-1] == "X":
-                    res -= 20
-            elif item == "D" or item == "M":
-                if stack and stack[-1] == "C":
-                    res -= 200
-            stack.append(item)
-        return res
+        pre_value = None
+        for ch in s:
+            if (ch in ["V", "X"] and pre_value == 1) or \
+               (ch in ["L", "C"] and pre_value == 10) or \
+               (ch in ["D", "M"] and pre_value == 100):
+                res += dic[ch] - 2 * pre_value 
+            else:
+                res += dic[ch]
+                pre_value = dic[ch]
+        return res

0256.粉刷房子/0256-粉刷房子.py

@@ -10,4 +10,4 @@ def minCost(self, costs):
             costs[i][0] += min(costs[i - 1][1], costs[i - 1][2])
             costs[i][1] += min(costs[i - 1][0], costs[i - 1][2])
             costs[i][2] += min(costs[i - 1][0], costs[i - 1][1])
-        return min(costs[-1])
+        return min(costs[-1]) 

0435.无重叠区间/0435-无重叠区间.py

@@ -0,0 +1,18 @@
+class Solution(object):
+    def eraseOverlapIntervals(self, intervals):
+        """
+        :type intervals: List[List[int]]
+        :rtype: int
+        """
+        if not intervals or not intervals[0]:
+            return 0
+
+        intervals = sorted(intervals, key = lambda x:x[1])
+        pre_end = intervals[0][1]
+        canAttendCnt = 1
+        for i in range(1, len(intervals)):
+            if intervals[i][0] >= pre_end: # start later than previous one end
+                canAttendCnt += 1
+                pre_end = intervals[i][1]
+        return len(intervals) - canAttendCnt
+

0452.用最少数量的箭引爆气球/0452-用最少数量的箭引爆气球.py

@@ -7,14 +7,12 @@ def findMinArrowShots(self, points):
         if not points or not points[0]:
             return 0
 
-        points.sort(key = lambda x:x[1])
-
-        arrow = points[0][1]
-
+        points = sorted(points, key = lambda x: x[1])
         res = 1
-        for point in points:
-            if arrow < point[0]:
+        pre_end = points[0][1]
+
+        for i in range(1, len(points)):
+            if points[i][0] > pre_end:
                 res += 1
-                arrow = point[1]
-        
-        return res
+                pre_end = points[i][1]
+        return res

0542.01矩阵/0542-01矩阵.py

@@ -1,43 +1,35 @@
-from collections import deque
 class Solution(object):
     def updateMatrix(self, matrix):
         """
         :type matrix: List[List[int]]
         :rtype: List[List[int]]
         """
+        from collections import deque
         if not matrix or not matrix[0]:
-            return matrix
+            return matrix 
         m, n = len(matrix), len(matrix[0])
-        res = matrix[:]
-        
-        q = deque()
-               
-        for i in range(m):
-            for j in range(n):
-                if matrix[i][j] == 0:
-                    q.append([[i, j], 0])
 
-        dx = [1, -1, 0, 0]        
+        dx = [1, -1, 0, 0]
         dy = [0, 0, 1, -1]
-        visited = [[0 for _ in range(n + 1)] for _ in range(m + 1)]
-
-        while q:
-            tmp, distance = q.popleft()
-            x0, y0 = tmp[0], tmp[1]
-
-            if matrix[x0][y0] == 1:
-                res[x0][y0] = distance
+        res = [[0 for _ in range(n)] for _ in range (m)]
+        for i in range(m):
+            for j in range(n):
+                if matrix[i][j] == 1:
+                    queue = deque([(i, j, 0)])
+                    visited = set((i, j))
+                    while queue:
+                        x, y, dist = queue.popleft()
 
-            for k in range(4):
-                x = x0 + dx[k]
-                y = y0 + dy[k]
+                        if matrix[x][y] == 0:
+                            res[i][j] = dist 
+                            break
+                        else:
+                            for k in range(4):
+                                xx = x + dx[k]
+                                yy = y + dy[k]
 
-                if 0 <= x < m and 0 <= y < n and visited[x][y] != 1:
-                    q.append([[x, y], distance + 1])
-                    visited[x][y] = 1
-        return res
-                    
-                    
-                    
-    
-            
+                                if 0 <= xx < m and 0 <= yy < n and (xx, yy) not in visited:
+                                    visited.add((xx, yy))
+                                    queue.append((xx, yy, dist + 1))
+        
+        return res

0881.救生艇/0881-救生艇.py

@@ -0,0 +1,22 @@
+class Solution(object):
+    def numRescueBoats(self, people, limit):
+        """
+        :type people: List[int]
+        :type limit: int
+        :rtype: int
+        """
+        people.sort()
+        left, right = 0, len(people) - 1
+        res = 0
+        while left <= right:
+            if left == right:
+                res += 1
+                break
+            if people[left] + people[right] <= limit:
+                left += 1
+                right -= 1
+                res += 1
+            else:
+                right -= 1
+                res += 1
+        return res