35. Search Insert Position (Array)

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

思路：排好序的数列用二分法进行搜索

class Solution {
public:
    int searchInsert(int A[], int n, int target) {
        if(n==0) return 0;
        binarySearch(A,0,n-1,target);
        return result;
    }

    void binarySearch(int A[], int start, int end, int target){ //find the first value >= target
    if(start== end){
        if(A[start] < target) result = start+1;
        else result = start;
        return;
    }
    int mid = start + ((end-start)>>1); //prevent overflow
    if(A[mid] < target) binarySearch(A,mid+1, end, target);
    else if(A[mid] > target) binarySearch(A,start, mid, target);
    else result = mid;
}
private:
    int result;
};