LeetCode - Array/Binary Search - Search Insert Position

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

class Solution {
public:
int searchInsert(int A[], int n, int target) {
// 时间复杂度为O(n)，空间复杂度为O(1)
if(A==NULL)
return 0;
size_t result=0;
for(;result<n;result++)
{
if(A[result]>=target) return result;
}
return result;
}
};

class Solution {
public:
int searchInsert(int A[], int n, int target) {
// 时间复杂度为O(lgn)，空间复杂度为O(1)
if(A==NULL||n==0)
return 0;
int beg=0, end=n-1, result=(beg+end)/2;
while(A[result]!=target)
{
if(A[result]>target)
{
end=result-1;
if(result>0)result--;
}
if(A[result]<target)beg=++result;
if(beg<=end)
result=(beg+end)/2;
else
break;
}
return result;
}
};