FirstPositionOfTarget.java

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// For a given sorted array (ascending order) and a target number, find the first index of this number in O(log n) time complexity.

// If the target number does not exist in the array, return -1.

// Example
// Example 1:
// 	Input:  [1,4,4,5,7,7,8,9,9,10]，1
// 	Output: 0
	
// 	Explanation: 
// 	the first index of  1 is 0.

// Example 2:
// 	Input: [1, 2, 3, 3, 4, 5, 10]，3
// 	Output: 2
	
// 	Explanation: 
// 	the first index of 3 is 2.

// Example 3:
// 	Input: [1, 2, 3, 3, 4, 5, 10]，6
// 	Output: -1
	
// 	Explanation: 
// 	Not exist 6 in array.

// Challenge
// If the count of numbers is bigger than 2^32, can your code work properly

public class Solution {
  /**
   * @param nums: The integer array.
   * @param target: Target to find.
   * @return: The first position of target. Position starts from 0.
   */
  public int binarySearch(int[] nums, int target) {
      // write your code here
  }
}