JavaScriptAlgorithmsAndDataStructuresMasterclass/divideAndConcuer.js at main · surohak/JavaScriptAlgorithmsAndDataStructuresMasterclass · GitHub

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function countZeroes(arr) {
  let left = 0;
  let right = arr.length - 1;

  while (left <= right) {
    const middle = Math.floor((left + right) / 2);

    if (arr[middle] === 1) left = middle + 1;
    else right = middle - 1;
  }

  return arr.length - left;
}

function sortedFrequency(arr, num) {
  let left = 0;
  let right = arr.length - 1;

  while (left <= right) {
    const middle = Math.floor((left + right) / 2);

    if (arr[middle] === num) {
      let leftCount = middle;
      let rightCount = middle;

      while (arr[leftCount] === num && leftCount >= 0) {
        leftCount--;
      }

      while (arr[rightCount] === num && rightCount < arr.length) {
        rightCount++;
      }

      return rightCount - leftCount - 1;
    }

    if (arr[middle] < num) left = middle + 1;
    else right = middle - 1;
  }

  return -1;
}

function findRotatedIndex(arr, num) {
  let left = 0;
  let right = arr.length - 1;

  if (right && arr[left] >= arr[right]) {
    let middle = Math.floor((left + right) / 2);

    while (arr[middle] <= arr[middle + 1]) {
      if (arr[left] <= arr[middle]) left = middle + 1;
      else right = middle - 1;

      middle = Math.floor((left + right) / 2);
    }

    if (num >= arr[0] && num <= arr[middle]) {
      left = 0;
      right = middle;
    } else {
      left = middle + 1;
      right = arr.length - 1;
    }
  }

  while (left <= right) {
    const middle = Math.floor((left + right) / 2);

    if (num === arr[middle]) return middle;

    if (num > arr[middle]) left = middle + 1;
    else right = middle - 1;
  }

  return -1;
}