#1732 - Find the Highest Altitude

EasyPrefix Sum

A biker starts a trip at altitude 0 and goes through n + 1 points. You are given an integer array gain of length n, where gain[i] is the net gain in altitude between points i and i + 1. Return the highest altitude reached.

Input	Output
gain = [-5,1,5,0,-7]	1
gain = [-4,-3,-2,-1,4,3,2]	0

Solution Space

Try it

/**
 * Returns the highest altitude reached during the trip.
 *
 * @param gain Net altitude change between consecutive points
 * @returns    Maximum altitude (starting altitude is 0)
 */
export function largestAltitude(gain: number[]): number {
  let altitude = 0;
  let max = 0;

  for (const g of gain) {
    altitude += g;
    if (altitude > max) max = altitude;
  }

  return max;
}

Approach: prefix sum – accumulate a running altitude and track the maximum seen so far.

Time: O(n) – single pass through the `gain` array.

Space: O(1) – two integer variables.

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