MD ARIFUL HAQUE

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# 1404. Number of Steps to Reduce a Number in Binary Representation to One

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;
}
}