# Codility: Flags Solution

*Lesson 10 Prime and Composite Numbers*

## Approach

(Flag is on the peak only)

Maximum number of peaks is upper bound of

Get an array of peaks to determine whether an index is peak

Decrease from max peaks, for each iteration, check if that the number of peak is valid

The number of peak is whether valid or not is based on the condition: distance between any 2 flag should be >= number of flags

## Implementation

1function solution(A) {2 const N = A.length3 const isPeak = (a, b, c) => a < b && b > c4 const checkFlagsValid = (flags, peaks) => {5 const N = peaks.length6 let flagsLeft = flags7 let i = 18 while (i < N - 1 && flagsLeft) {9 if (peaks[i]) {10 flagsLeft -= 111 i += flags12 } else {13 i += 114 }15 }16 return flagsLeft === 017 }1819 const peaks = Array(N).fill(false)20 let peaksCount = 021 for (let i = 1; i < N - 1; i++) {22 if (isPeak(A[i - 1], A[i], A[i + 1])) {23 peaksCount++24 peaks[i] = true25 }26 }2728 let maxFlags = Math.min(Math.ceil(Math.sqrt(N)), peaksCount)29 while (maxFlags) {30 if (checkFlagsValid(maxFlags, peaks)) {31 break32 }33 maxFlags--34 }35 return maxFlags36}

## References

## Comments

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## Tags

codility

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