Add 171

Author: ChienkuChen

src/_171/171.excel-sheet-column-number.java

@@ -0,0 +1,21 @@
+package _171;
+
+class Solution {
+    public int titleToNumber(String s) {
+        // the ASCII code of A is 65
+
+        int sum = 0;
+        for (int i = 0; i < s.length(); i++) {
+            sum += Math.pow(26, s.length() - 1 - i) * (s.charAt(i) - 64);
+        }
+
+        return sum;
+    }
+
+    public static void main(String[] args) {
+        System.out.println(new Solution().titleToNumber("A"));
+        System.out.println(new Solution().titleToNumber("AB"));
+        System.out.println(new Solution().titleToNumber("ZY"));
+        System.out.println(new Solution().titleToNumber("AZ"));
+    }
+}