Create PrefixSum.cpp

PrefixSum.cpp

@@ -0,0 +1,51 @@
+/*
+
+Given an array of N integers
+Given Q queries
+In each query given a range, L and R
+Print the sum of array elements from L to R (inclusive) 
+
+Constratints:
+1 <= N <= 10^5
+1 <= a[i] <= 10^9
+1 <= Q <= 10^5
+1 <= L , R <= N
+
+*/
+
+#include <bits/stdc++.h>
+using namespace std;
+
+const int N = 1e5 + 10;
+int a[N];
+int prefixSum[N];
+
+int main()
+{
+
+    int n;
+    cin >> n;
+
+    // NOTE: Take input from 1 in prefix sum
+    for (int i = 1; i <= n; i++)
+        cin >> a[i];
+
+    // Pre computing
+    for (int i = 1; i <= n; i++)
+        prefixSum[i] = prefixSum[i - 1] + a[i];
+
+    int q;
+    cin >> q;
+
+    while (q--)
+    {
+
+        int l, r;
+        cin >> l >> r;
+
+        cout << prefixSum[r] - prefixSum[l - 1] << endl;
+    }
+
+    // Time complexity:
+    // O(N) + O(Q) = O(10^5)
+}