Question
Formatted question description: https://leetcode.ca/all/1099.html
Given an array A of integers and integer K,
return the maximum S such that there exists
i < j with
A[i] + A[j] = S and
S < K.
If no i, j, exist satisfying this equation, return -1.
Example 1:
Input: A = [34,23,1,24,75,33,54,8], K = 60
Output: 58
Explanation:
We can use 34 and 24 to sum 58 which is less than 60.
Example 2:
Input: A = [10,20,30], K = 15
Output: -1
Explanation:
In this case it's not possible to get a pair sum less that 15.
Note:
1 <= A.length <= 100
1 <= A[i] <= 1000
1 <= K <= 2000
Algorithm
(brute force) O(n^2)
Enumerate i and j, and then find the maximum value less than K.
time complexity
- Two-level loop traversal, so the time complexity is O(n^2)).
Space complexity
- Only a constant number of traversals are needed, so the space complexity is O(1).
Code
Java
import java.util.Arrays;
public class Two_Sum_Less_Than_K {
class Solution {
public int twoSumLessThanK(int[] A, int K) {
int res = -1;
if(A == null || A.length == 0){
return res;
}
Arrays.sort(A);
int l = 0;
int r = A.length-1;
while(l<r){
int sum = A[l] + A[r];
if(sum < K){
res = Math.max(res, sum);
l++;
}else{
r--;
}
}
return res;
}
}
}