You have a 1-indexed binary string of length n where all the bits are 0 initially. We will flip all the bits of this binary string (i.e., change them from 0 to 1) one by one. You are given a 1-indexed integer array flips where flips[i] indicates that the bit at index i will be flipped in the ith step.
A binary string is prefix-aligned if, after the ith step, all the bits in the inclusive range [1, i] are ones and all the other bits are zeros.
Return the number of times the binary string is prefix-aligned during the flipping process.
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Example 1:
\n\n\nInput: flips = [3,2,4,1,5]\nOutput: 2\nExplanation: The binary string is initially "00000".\nAfter applying step 1: The string becomes "00100", which is not prefix-aligned.\nAfter applying step 2: The string becomes "01100", which is not prefix-aligned.\nAfter applying step 3: The string becomes "01110", which is not prefix-aligned.\nAfter applying step 4: The string becomes "11110", which is prefix-aligned.\nAfter applying step 5: The string becomes "11111", which is prefix-aligned.\nWe can see that the string was prefix-aligned 2 times, so we return 2.\n\n\n
Example 2:
\n\n\nInput: flips = [4,1,2,3]\nOutput: 1\nExplanation: The binary string is initially "0000".\nAfter applying step 1: The string becomes "0001", which is not prefix-aligned.\nAfter applying step 2: The string becomes "1001", which is not prefix-aligned.\nAfter applying step 3: The string becomes "1101", which is not prefix-aligned.\nAfter applying step 4: The string becomes "1111", which is prefix-aligned.\nWe can see that the string was prefix-aligned 1 time, so we return 1.\n\n\n
\n
Constraints:
\n\nn == flips.length1 <= n <= 5 * 104flips is a permutation of the integers in the range [1, n].Compiled with clang 11 using the latest C++ 17 standard.
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