end of day 4 week 1

week 1/day 4/exo5.md

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+**Task:**
+
+* Explain what happens if the number of users doubles
+* Write the runtime formula using:
+
+  * `n` = number of users
+  * `m` = average username length
+
+**Expected reasoning:**
+
+* Doubling the list doubles the execution time
+* Linear runtime: `T(n, m) = n × m`
+
+**Answer**
+
+if the number of user double in size 
+
+$$
+T(2n, m) = n /times 2 /times m
+$$
+
+so the number of execution will multiply by 2
+
+the big O notation will be O(n⋅m)