Search Insert Position

题目：

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.

Here are few examples.
[1,3,5,6], 5 → 2
[1,3,5,6], 2 → 1
[1,3,5,6], 7 → 4
[1,3,5,6], 0 → 0

解题思路：

 1 /**
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 6  */
 7 
 8 // version 1: find the first position >= target
 9 public class Solution {
10     public int searchInsert(int[] A, int target) {
11         if (A == null || A.length == 0) {
12             return 0;
13         }
14         int start = 0, end = A.length - 1;
15         
16         while (start + 1 < end) {
17             int mid = start + (end - start) / 2;
18             if (A[mid] == target) {
19                 return mid;
20             } else if (A[mid] < target) {
21                 start = mid;
22             } else {
23                 end = mid;
24             }
25         }
26         
27         if (A[start] >= target) {
28             return start;
29         } else if (A[end] >= target) {
30             return end;
31         } else {
32             return end + 1;
33         }
34     }
35 }
36 
37 // version 2: find the last position < target, return +1
38 
39 public class Solution {
40     public int searchInsert(int[] A, int target) {
41         if (A == null || A.length == 0) {
42             return 0;
43         }
44         int start = 0;
45         int end = A.length - 1;
46         int mid;
47         
48         if (target < A[0]) {
49             return 0;
50         }
51         // find the last number less than target
52         while (start + 1 < end) {
53             mid = start + (end - start) / 2;
54             if (A[mid] == target) {
55                 return mid;
56             } else if (A[mid] < target) {
57                 start = mid;
58             } else {
59                 end = mid;
60             }
61         }
62         
63         if (A[end] == target) {
64             return end;
65         }
66         if (A[end] < target) {
67             return end + 1;
68         }
69         if (A[start] == target) {
70             return start;
71         }
72         return start + 1;
73     }
74 }