Sam and Subtrings

Data Structure Algo/C++/sam_and_subtrings.cpp.txt

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+/** Sam and substrings
+    https://www.hackerrank.com/challenges/sam-and-substrings/problem
+*/
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+/*
+ * Complete the 'substrings' function below.
+ *
+ * The function is expected to return an INTEGER.
+ * The function accepts STRING n as parameter.
+ */
+
+long long substrings(string n) {
+    long long sum = 0;
+    long curelem;
+    long mod = 1000000007;
+    long long ones = 1;
+    for (long i = n.size () -1 ; i >=0; --i) {
+        curelem = n[i] - '0';
+        sum += ((curelem * (i + 1) * ones)% 1000000007) ;
+        ones = ((ones * 10) + 1) % mod;
+        sum %= 1000000007;
+    }
+    return sum;
+}
+
+int main()
+{
+    ofstream fout(getenv("OUTPUT_PATH"));
+
+    string n;
+    getline(cin, n);
+
+    long long result = substrings(n);
+
+    fout << result << "\n";
+
+    fout.close();
+
+    return 0;
+}