Arrays and Iteration

Find Maximum

Scan the array once, keeping the largest value seen so far. The replay highlights when a candidate replaces the running maximum.

Algorithm

execution replay The checked-in replay follows the language-neutral state table for `array-find-max`.
cross-language comparison This TypeScript DSA version keeps the same data and final output as every other DSA book in this wave.

Basic Implementation

basic.ts
Replay: real traced execution (multi-file project)
const arr: number[] = [3, 1, 4, 1, 5, 9, 2, 6];
let best: number = arr[0];
for (let i = 1; i < arr.length; i++) {
  if (arr[i] > best) {
    best = arr[i];
  }
}
console.log(best);

  1. arr ← [3, 1, 4, 1, 5, 9, 2, 6], best ← 3

    1const arr: number[] = [3, 1, 4, 1, 5, 9, 2, 6];2let best: number = arr[0];
    values this step[3, 1, 4, 1, 5, 9, 2, 6]arr3best

  2. replaced ← no

    3for (let i = 1; i < arr.length; i++) {4  if (arr[i] > best) {5    best = arr[i];
    values this stepnoreplaced1i1arr[i]3best

  3. best ← 4, replaced ← yes

    3for (let i = 1; i < arr.length; i++) {4  if (arr[i] > best) {5    best = arr[i];
    values this step3 → 4bestyesreplaced2i4arr[i]

  4. replaced ← no

    3for (let i = 1; i < arr.length; i++) {4  if (arr[i] > best) {5    best = arr[i];
    values this stepnoreplaced3i1arr[i]4best

  5. best ← 5, replaced ← yes

    3for (let i = 1; i < arr.length; i++) {4  if (arr[i] > best) {5    best = arr[i];
    values this step4 → 5bestyesreplaced4i5arr[i]

  6. best ← 9, replaced ← yes

    3for (let i = 1; i < arr.length; i++) {4  if (arr[i] > best) {5    best = arr[i];
    values this step5 → 9bestyesreplaced5i9arr[i]

  7. replaced ← no

    3for (let i = 1; i < arr.length; i++) {4  if (arr[i] > best) {5    best = arr[i];
    values this stepnoreplaced6i2arr[i]9best

  8. replaced ← no

    3for (let i = 1; i < arr.length; i++) {4  if (arr[i] > best) {5    best = arr[i];
    values this stepnoreplaced7i6arr[i]9best

  9. stdout ← 9

    1const arr: number[] = [3, 1, 4, 1, 5, 9, 2, 6];2let best: number = arr[0];
    values this step9stdout9best

Complexity

  • Time: O(n)
  • Space: O(1)

Implementation notes

  • TypeScript declares the input as const arr: number[] and the running value as let best: number, so the checked source scans finite JavaScript Number values through TypeScript's number type.
  • The implementation uses an indexed for loop rather than reduce, so the state stays in the local best binding seeded from arr[0], with arr[i] as the current value.
  • Each arr[i] > best comparison is numeric. When true, best = arr[i] rebinds the local number; the array itself is never mutated.
  • The replay shows replacements at i=2 (4), i=4 (5), and i=5 (9), while values 1, 1, 2, and 6 leave best unchanged.
  • console.log(best) prints 9. Aside from the initial number[], the scan only updates scalar bindings and creates no lesson-visible heap allocation.