On a broken calculator that has a number showing on its display, we can perform two operations:
- Double: Multiply the number on the display by 2, or;
- Decrement: Subtract 1 from the number on the display.
Initially, the calculator is displaying the number X.
Return the minimum number of operations needed to display the number Y.
Example 1:
Input: X = 2, Y = 3
Output: 2
Explanation: Use double operation and then decrement operation {2 -> 4 -> 3}.
Example 2:
Input: X = 5, Y = 8
Output: 2
Explanation: Use decrement and then double {5 -> 4 -> 8}.
Example 3:
Input: X = 3, Y = 10
Output: 3
Explanation: Use double, decrement and double {3 -> 6 -> 5 -> 10}.
Example 4:
Input: X = 1024, Y = 1
Output: 1023
Explanation: Use decrement operations 1023 times.
Runtime: 4 ms, faster than 100.00% of C++ online submissions for Broken Calculator.
Memory Usage: 4.7 MB, less than 100.00% of C++ online submissions for Broken Calculator.
class Solution { public: int brokenCalc(int X, int Y) { if(X == Y) return 0; if(X < Y) { if(Y&1 == 1) { int tmp = ((Y >> 1)+1) << 1; return brokenCalc(X,tmp >> 1) + tmp - Y + 1; }else { return brokenCalc(X,Y>>1)+1; } } return X - Y; } };