Create 975-odd-even-jump.js

Author: everthis

975-odd-even-jump.js

@@ -0,0 +1,52 @@
+/**
+ * @param {number[]} A
+ * @return {number}
+ */
+const oddEvenJumps = function (A) {
+  // Creates an array with ONLY the indices of the sorted array
+  let sorted = A.map((el, idx) => idx).sort((a, b) => A[a] - A[b] || a - b)
+  // Create an array of '-1's of the same array length for odd and even jumps
+  let oddJumps = new Array(A.length).fill(-1)
+  let evenJumps = new Array(A.length).fill(-1)
+  // Create an empty stack
+  let stack = []
+  // Loop the the sorted array of the indices
+  for (let i of sorted) {
+    // Loops as long the stack is full OR if the index is greater than the the last index of the stack
+    while (stack.length && i > stack[stack.length - 1]) {
+      // Pops the index from the stack and place and add the 'i' index in sortedJumps
+      oddJumps[stack.pop()] = i
+    }
+    // Pushes the index onto the stack
+    stack.push(i)
+  }
+  // Empty the stack
+  stack = []
+  // Reverses the sorted index array
+  let reverseSorted = sorted.sort((a, b) => A[b] - A[a] || a - b)
+  // Does the exact thing but for even jumps
+  for (let i of reverseSorted) {
+    while (stack.length && i > stack[stack.length - 1]) {
+      evenJumps[stack.pop()] = i
+    }
+    stack.push(i)
+  }
+  // Starts the count at 0
+  let count = 1
+  // Creates a boolean array of false elements for even and odd ends
+  let oddEnd = new Array(A.length).fill(false)
+  let evenEnd = new Array(A.length).fill(false)
+  // Switches the end of each array to true
+  oddEnd[A.length - 1] = true
+  evenEnd[A.length - 1] = true
+  // Loops through the array, starting from the 2nd from the right (since we do not need to worry about       the last index)
+  for (let i = A.length - 2; i >= 0; --i) {
+    // If even jumps does
+    if (evenJumps[i] !== -1 && oddEnd[evenJumps[i]]) evenEnd[i] = true
+    if (oddJumps[i] !== -1 && evenEnd[oddJumps[i]]) {
+      oddEnd[i] = true
+      count++
+    }
+  }
+  return count
+}