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Commit df17e29

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Add backtracking solution to JumpGame.
1 parent aacd779 commit df17e29

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4 files changed

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import btJumpGame from '../btJumpGame';
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describe('btJumpGame', () => {
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it('should solve Jump Game problem in backtracking manner', () => {
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expect(btJumpGame([1, 0])).toBeTruthy();
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expect(btJumpGame([100, 0])).toBeTruthy();
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expect(btJumpGame([2, 3, 1, 1, 4])).toBeTruthy();
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expect(btJumpGame([1, 1, 1, 1, 1])).toBeTruthy();
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expect(btJumpGame([1, 1, 1, 10, 1])).toBeTruthy();
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expect(btJumpGame([1, 5, 2, 1, 0, 2, 0])).toBeTruthy();
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expect(btJumpGame([1, 0, 1])).toBeFalsy();
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expect(btJumpGame([3, 2, 1, 0, 4])).toBeFalsy();
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expect(btJumpGame([0, 0, 0, 0, 0])).toBeFalsy();
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expect(btJumpGame([5, 4, 3, 2, 1, 0, 0])).toBeFalsy();
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});
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});

‎src/algorithms/uncategorized/jump-game/__test__/grdJumpGame.test.js‎

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expect(grdJumpGame([100, 0])).toBeTruthy();
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expect(grdJumpGame([2, 3, 1, 1, 4])).toBeTruthy();
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expect(grdJumpGame([1, 1, 1, 1, 1])).toBeTruthy();
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expect(grdJumpGame([1, 1, 1, 10, 1])).toBeTruthy();
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expect(grdJumpGame([1, 5, 2, 1, 0, 2, 0])).toBeTruthy();
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expect(grdJumpGame([1, 0, 1])).toBeFalsy();
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/**
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* BACKTRACKING approach of solving Jump Game.
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*
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* @param {number[]} numbers - array of possible jump length.
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* @param {number} startIndex - index from where we start jumping.
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* @param {number[]} currentJumps - current jumps path.
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* @return {boolean}
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*/
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export default function btJumpGame(numbers, startIndex = 0, currentJumps = []) {
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if (startIndex === numbers.length - 1) {
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// We've jumped directly to last cell. This situation is a solution.
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return true;
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}
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// Check what the longest jump we could make from current position.
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// We don't need to jump beyond the array.
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const maxJumpLength = Math.min(
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numbers[startIndex], // Jump is within array.
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numbers.length - 1 - startIndex, // Jump goes beyond array.
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);
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// Let's start jumping from startIndex and see whether any
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// jump is successful and has reached the end of the array.
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for (let jumpLength = maxJumpLength; jumpLength > 0; jumpLength -= 1) {
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// Try next jump.
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const nextIndex = startIndex + jumpLength;
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currentJumps.push(nextIndex);
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const isJumpSuccessful = btJumpGame(numbers, nextIndex, currentJumps);
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// Check if current jump was successful.
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if (isJumpSuccessful) {
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return true;
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}
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// BACKTRACKING.
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// If previous jump wasn't successful then retreat and try the next one.
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currentJumps.pop();
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}
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return false;
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}

‎src/algorithms/uncategorized/jump-game/grdJumpGame.js‎

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* GREEDY approach of solving Jump Game.
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*
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* @param {number[]} numbers - array of possible jump length.
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* @return {boolean}
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*/
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export default function grdJumpGame(numbers) {
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// The "good" cell is a cell from which we may jump to the last cell of the numbers array.

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