Given an array of n integers nums and a target, find the number of index triplets i, j, k
with 0 <= i < j < k < n
that satisfy the condition nums[i] + nums[j] + nums[k] < target
.
For example, given nums = [-2, 0, 1, 3]
, and target = 2.
Return 2. Because there are two triplets which sums are less than 2:
[-2, 0, 1] [-2, 0, 3]
Follow up:
Could you solve it in O(n2) runtime?
Solution:
public class Solution { public int threeSumSmaller(int[] nums, int target) { if (nums.length<3) return 0; Arrays.sort(nums); int count = 0; for (int p1=0;p1<nums.length-2;p1++){ // Early termination if (nums[p1]+nums[p1+1]+nums[p1+2]>=target) break; int p2=p1+1, p3=nums.length-1; while (p2<p3){ while (p2<p3 && nums[p2]+nums[p3]>=target-nums[p1]){ p3--; } count += p3-p2; p2++; } } return count; } }