LeetCode--Search Insert Position

Search Insert Position

Total Accepted: 14091 Total
Submissions: 41005My Submissions

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) {
        //if()
        /*
        int m;
        int x=0;
        int y=n;
        while(x<y)
        {
            m=x+(y-x)/2;
            if(A[m]==target)return m;
            else if(A[m]>target)y=m;
            else x=m+1;
        }
        return m+1;
        */
        int m;
        int x=0;
        int y=n;
        while(x<y)
        {
            m=x+(y-x)/2;
            if(A[m]>=target)y=m;
            else x=m+1;
        }
        return x;
    }
};

二分找查求下界

int lower_bound(int *A,int x,int y,int v)
{
      int m;
      while(x<y)
      {
              m=x+(y-x)/2;
              if(A[m]>=v)y=m;
              else x=m+1;
      }
      return x;
}

求上界时

只需要将 if(A[m]>=v)y=m;else x=m+1; 改成if(A[m]<=v)x=m+1;else y=m;