Range update

algos/range_queries/DifferenceArray/soln/IshanRajSingh/Solution1.py

@@ -0,0 +1,39 @@
+# Approach: use difference array with Fenwick Tree to support range add and point query
+# Runtime: O((n+q) log n)
+import sys
+input=sys.stdin.readline
+
+class BIT:
+    def __init__(self,n):
+        self.n=n
+        self.bit=[0]*(n+1)
+    def add(self,i,v):
+        while i<=self.n:
+            self.bit[i]+=v
+            i+=i&-i
+    def sum(self,i):
+        s=0
+        while i>0:
+            s+=self.bit[i]
+            i-=i&-i
+        return s
+
+n,q=map(int,input().split())
+arr=list(map(int,input().split()))
+bit=BIT(n)
+for i in range(n):
+    bit.add(i+1,arr[i])
+    bit.add(i+2,-arr[i])
+
+out=[]
+for _ in range(q):
+    qry=list(map(int,input().split()))
+    if qry[0]==1:
+        _,a,b,u=qry
+        bit.add(a,u)
+        bit.add(b+1,-u)
+    else:
+        _,k=qry
+        out.append(str(bit.sum(k)))
+
+print("\n".join(out))