1404. Number of Steps to Reduce a Number in Binary Representation to One
Medium
Given the binary representation of an integer as a string s
, return the number of steps to reduce it to 1
under the following rules:
 If the current number is even, you have to divide it by
2
.  If the current number is odd, you have to add
1
to it.
It is guaranteed that you can always reach one for all test cases.
Example 1:
 Input: "1101"
 Output: 6

Explanation: "1101" corressponds to number 13 in their decimal representation.
 Step 1) 13 is odd, add 1 and obtain 14.
 Step 2) 14 is even, divide by 2 and obtain 7.
 Step 3) 7 is odd, add 1 and obtain 8.
 Step 4) 8 is even, divide by 2 and obtain 4.
 Step 5) 4 is even, divide by 2 and obtain 2.
 Step 6) 2 is even, divide by 2 and obtain 1.
Example 2:
 Input: s = "10"
 Output: 1

Explanation: "10" corressponds to number 2 in their decimal representation.
 Step 1) 2 is even, divide by 2 and obtain 1.
Example 3:
 Input: s = "1"
 Output: 0
Constraints:
1 <= s.length <= 500

s
consists of characters '0' or '1' s[0] == '1'
Solution:
class Solution {
/**
* @param String $s
* @return Integer
*/
function numSteps($s) {
$ans = 0;
while ($s[strlen($s)  1] == '0') {
$s = substr($s, 0, 1);
++$ans;
}
if ($s == "1") return $ans;
++$ans;
for ($i = 0; $i < strlen($s); $i++) {
$ans += $s[$i] == '1' ? 1 : 2;
}
return $ans;
}
}
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