Add Excel Sheet Column Number

Author: rp-code9

README.md

@@ -196,6 +196,7 @@ Princeton Algorithms [Part 1](https://www.coursera.org/learn/algorithms-part1/)
     * Recursive [C++](problems/math/PascalTriangle.cpp)
     * Iterative [C++](problems/math/PascalTriangle.cpp)
 * Happy number [Wiki](https://en.wikipedia.org/wiki/Happy_number) [C++](problems/math/HappyNumber.cpp)
+* Excel Sheet Column Number [C++](problems/math/SheetColumnNumber.cpp)
 
 ## Permutation
 * Permutation of objects [Java](problems/queue/Permutation.java)

problems/math/SheetColumnNumber.cpp

@@ -0,0 +1,32 @@
+// Leetcode https://leetcode.com/explore/interview/card/top-interview-questions-medium/113/math/817/
+
+#include <iostream>
+#include <string>
+#include <vector>
+
+const int BASE = 26;
+
+int titleToNumber(const std::string& columnTitle)
+{
+    int number = 0;
+    for (auto ch : columnTitle) {
+        number = number * BASE + (ch - 'A' + 1);
+    }
+    return number;
+}
+
+void test(const std::string& columnTitle)
+{
+    std::cout << "Column title : " << columnTitle << " , number : " << titleToNumber(columnTitle) << "\n";
+    std::cout << "=====================================\n";
+}
+
+int main()
+{
+    test("A");
+    test("AB");
+    test("ZY");
+    test("FXSHRXW");
+
+    return 0;
+}