Added : Find First and Last Position of Element in Sorted Array

Author: rohitkumar-rk

LeetCode/Array/34. Find First and Last Position of Element in Sorted Array/Problem Statement.txt

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+Given an array of integers nums sorted in ascending order, find the starting and ending position of a given target value.
+
+Your algorithm's runtime complexity must be in the order of O(log n).
+
+If the target is not found in the array, return [-1, -1].
+
+Example 1:
+
+Input: nums = [5,7,7,8,8,10], target = 8
+Output: [3,4]
+Example 2:
+
+Input: nums = [5,7,7,8,8,10], target = 6
+Output: [-1,-1]
+ 
+
+Constraints:
+
+0 <= nums.length <= 10^5
+-10^9 <= nums[i] <= 10^9
+nums is a non decreasing array.
+-10^9 <= target <= 10^9

LeetCode/Array/34. Find First and Last Position of Element in Sorted Array/Solution.java

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+/*
+@lc id : 34
+@problem : Find First and Last Position of Element in Sorted Array
+@author : rohit
+@url : https://leetcode.com/problems/find-first-and-last-position-of-element-in-sorted-array/
+@difficulty : medium
+*/
+
+class Solution {
+    
+    public int findEndingIndex(int[] nums, int target){
+        int index = -1;
+        int start = 0;
+        int end = nums.length - 1;
+        
+        while(start <= end){
+            int mid = start + (end - start) / 2;
+            
+            if(nums[mid] == target)
+                index = mid;
+            
+            if(nums[mid] <= target)
+                start = mid + 1;
+            else end = mid - 1;
+        }
+            
+        
+        
+        
+        return index;
+    }
+    
+    public int findStartingIndex(int[] nums, int target){
+        int index = -1;
+        
+        int start = 0;
+        int end = nums.length - 1;
+        
+        while(start <= end){
+            int mid = start +  (end - start) / 2;
+            if(nums[mid]  == target)
+                index = mid;
+            
+            //If we have found target, still we want to go on left side
+            //If we haven't found, and target is smaller than mid, go left
+            if(nums[mid] >= target)
+                end = mid - 1;
+            
+            else start = mid + 1;
+        }
+        
+        return index;
+    }
+    
+    public int[] searchRange(int[] nums, int target) {
+        
+        int[] result  = new int[2];
+        result[0] = findStartingIndex(nums, target);
+        result[1] = findEndingIndex(nums, target);
+        return result;
+    }
+}