forked from mberktas/javascript-algorithms
-
Notifications
You must be signed in to change notification settings - Fork 0
/
backtrackingJumpGame.js
48 lines (42 loc) · 1.64 KB
/
backtrackingJumpGame.js
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
/**
* BACKTRACKING approach of solving Jump Game.
*
* This is the inefficient solution where we try every single jump
* pattern that takes us from the first position to the last.
* We start from the first position and jump to every index that
* is reachable. We repeat the process until last index is reached.
* When stuck, backtrack.
*
* @param {number[]} numbers - array of possible jump length.
* @param {number} startIndex - index from where we start jumping.
* @param {number[]} currentJumps - current jumps path.
* @return {boolean}
*/
export default function backtrackingJumpGame(numbers, startIndex = 0, currentJumps = []) {
if (startIndex === numbers.length - 1) {
// We've jumped directly to last cell. This situation is a solution.
return true;
}
// Check what the longest jump we could make from current position.
// We don't need to jump beyond the array.
const maxJumpLength = Math.min(
numbers[startIndex], // Jump is within array.
numbers.length - 1 - startIndex, // Jump goes beyond array.
);
// Let's start jumping from startIndex and see whether any
// jump is successful and has reached the end of the array.
for (let jumpLength = maxJumpLength; jumpLength > 0; jumpLength -= 1) {
// Try next jump.
const nextIndex = startIndex + jumpLength;
currentJumps.push(nextIndex);
const isJumpSuccessful = backtrackingJumpGame(numbers, nextIndex, currentJumps);
// Check if current jump was successful.
if (isJumpSuccessful) {
return true;
}
// BACKTRACKING.
// If previous jump wasn't successful then retreat and try the next one.
currentJumps.pop();
}
return false;
}