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September 25, 2016 19:24
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For this exercise, write two functions, reverseArray and reverseArrayInPlace. The first, reverseArray, takes an array as argument and produces a new array that has the same elements in the inverse order. The second, reverseArrayInPlace, does what the reverse method does: it modifies the array given as argument in order to reverse its elements. N…
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function reverseArray( arrayToInvert ) { | |
// create a variable for the new array | |
var invertedArray = []; | |
// count how many things are in the original array | |
numLoops = arrayToInvert.length; | |
// loop that many times backwards and put each element into the new array | |
for ( i = numLoops -1; i >= 0; i-- ) { | |
invertedArray.push( arrayToInvert[i]); | |
} | |
// return the inverted array | |
return invertedArray; | |
} | |
function reverseArrayInPlace( arrayToInvert ) { | |
// calculate the length of the array | |
invertArrayLength = arrayToInvert.length; | |
// calculate half the length of the array | |
numLoops = Math.floor( invertArrayLength / 2 ); | |
// loop that many times and swap the first and last elements | |
for ( i = 0; i < numLoops; i++ ) { | |
// hold on to the current number | |
var holdNum = arrayToInvert[i]; | |
// get the position of the swap number | |
var swapPos = invertArrayLength - 1 - i; | |
// replace the current number with the swap number | |
arrayToInvert[i] = arrayToInvert[swapPos]; | |
// put the hold number into the swap number | |
arrayToInvert[swapPos] = holdNum; | |
} | |
// return the inverted array | |
return arrayToInvert; | |
} | |
console.log(reverseArray(["A", "B", "C"])); | |
// → ["C", "B", "A"]; | |
var arrayValue = [1, 2, 3, 4, 5]; | |
reverseArrayInPlace(arrayValue); | |
console.log(arrayValue); | |
// → [5, 4, 3, 2, 1] |
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