34. Find First and Last Position of Element in Sorted Array

Problem Statement

Pattern: Binary Search

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Solution

static int search(int[] nums, int target, boolean findLeft) {  
   int start = 0, end = nums.length - 1, mid ans = -1;  
   // find left-most occurrence  
   while (start <= end) {  
      mid = start + (end - start) / 2;  
      if (nums[mid] < target) start = mid + 1;  
      else if (nums[mid] > target) end = mid - 1;  
         // if target found  
      else {  
         ans = mid;   // update ans  
         if (findLeft) end = mid - 1;  // keep searching left of mid  
         else start = mid + 1;       // keep searching right of mid  
      }  
   }  
   return ans;  
}  
  
public static int[] searchRange(int[] nums, int target) {  
   int[] ans = {-1, -1};  
   ans[0] = search(nums, target, true);  
   ans[1] = search (nums, target, false);  
   return ans;  
}

Notes