[변지협] Day27

leetcode3/변지협/v2/3701. Compute Alternating Sum.py

@@ -0,0 +1,20 @@
+'''
+1. 아이디어 :
+그냥 홀짝 더함
+
+2. 시간복잡도 :
+O(n)
+
+3. 자료구조/알고리즘 :
+'''
+class Solution:
+    def alternatingSum(self, nums: List[int]) -> int:
+        n = len(nums)
+        ans = 0
+        for i in range(n):
+            if i % 2 == 0:
+                ans += nums[i]
+            else:
+                ans -= nums[i]
+
+        return ans

leetcode3/변지협/v2/785. Is Graph Bipartite?.py

@@ -0,0 +1,53 @@
+'''
+그래프 그리다가 못풀었음.
+'''
+
+class Solution:
+    def isBipartite(self, graph: List[List[int]]) -> bool:
+        set_a, set_b = set(),set()
+
+        n = len(graph)
+        tmp = 0
+        while True:
+            # print('graph, tmp, set_a, set_b:', graph, tmp,set_a,set_b)
+            if all([len(g) == 0 for g in graph]):
+                break
+
+            if len(graph[tmp]) == 0:
+                if n-1 == tmp:
+                    tmp = 0
+                    continue
+                else:
+                    tmp += 1
+                    continue
+
+            element = graph[tmp].pop()
+            graph[element].remove(tmp)
+
+            if element in set_a and tmp in set_a:
+                return False
+
+            if element in set_b and tmp in set_b:
+                return False
+
+            if element in set_a:
+                set_b.add(tmp)
+                continue
+            elif element in set_b:
+                set_a.add(tmp)
+                continue
+            elif tmp in set_a:
+                set_b.add(element)
+                continue
+            elif tmp in set_b:
+                set_a.add(element)
+                continue
+
+            set_a.add(tmp)
+            set_b.add(element)
+            tmp = element
+
+        print('graph, tmp, set_a, set_b:', graph, tmp,set_a,set_b)
+
+        return True
+