added plus one solution. most asked technical question

Author: YOGENDERSS

LeetcodeProblems/Algorithms/plusone.java

@@ -0,0 +1,17 @@
+class Solution {
+    public int[] plusOne(int[] digits) {
+
+        for(int i = digits.length-1; i>=0; i--){
+            if (digits[i]<9){
+                digits[i]++;
+              return digits;
+            }       
+             digits[i]=0;
+
+           }
+       digits = new int[digits.length+1];
+        digits[0] = 1;
+        return digits; 
+ 
+    }
+}