35.Search-Insert-Position

35. Search Insert Position

题目地址

http://www.lintcode.com/problem/search-insert-position/description

https://www.jiuzhang.com/solutions/search-insert-position/

题目描述

Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.

You may assume NO duplicates in the array.

Example
[1,3,5,6], 5 → 2

[1,3,5,6], 2 → 1

[1,3,5,6], 7 → 4

[1,3,5,6], 0 → 0

Challenge
O(log(n)) time

代码

Appraoch 1: Find the first position

public class Solution {
    public int searchInsert(int[] A, int target) {
    if (A == null | A.length == 0) return 0;

    int start = 0;
    int end = A.length - 1;

    while (start + 1 < end) {
      int mid = start + (end - start) / 2;
      if (A[mind] == target) {
        return mid;
      } else if (A[mid] < target) {
        start = mid;
      } else {
        end = mid;
      }
    }

    if (A[start] >= target) {
      return start;
    } else if (A[end] >= target) {
      return end;
    } else {
      return end + 1;
    }

    /// approach 2:
    if (target < A[0]) return 0;

    if (A[end] == target) return end;
    if (A[start] == target) return start;
    if (A[end] < target)    return end + 1;

    return start + 1;

  }

}