[LintCode] 3Sum Smaller

AprilJ 发布于2019-08-15 18:09 / 802人阅读

Problem

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.

Example

Given nums = [-2,0,1,3], target = 2, return 2.

Explanation:

Because there are two triplets which sums are less than 2:
[-2, 0, 1]
[-2, 0, 3]

Challenge

Could you solve it in O(n2) runtime?

Solution

public class Solution {
    /**
     * @param nums:  an array of n integers
     * @param target: a target
     * @return: the number of index triplets satisfy the condition nums[i] + nums[j] + nums[k] < target
     */
    public int threeSumSmaller(int[] nums, int target) {
        // Write your code here
        if (nums.length < 3) return 0;
        Arrays.sort(nums);
        if (nums[0] >= target) return 0;
        int count = 0;
        for (int i = 0; i < nums.length-2; i++) {
            int start = i+1, end = nums.length-1;
            int sum = target - nums[i];
            while (start < end) {
                if (nums[start] + nums[end] < sum) {
                    count += end-start;
                    start++;
                } else {
                    end--;
                }
            }
        }
        return count;
    }
}

超融合服务器服务器托管 Smaller LintCode LintCode134_LRU

文章版权归作者所有，未经允许请勿转载,若此文章存在违规行为，您可以联系管理员删除。

转载请注明本文地址：https://www.ucloud.cn/yun/69649.html

[Leetcode] 3Sum Smaller 三数较小和

摘要：排序法复杂度时间空间思路解题思路和一样，也是先对整个数组排序，然后一个外层循环确定第一个数，然后里面使用头尾指针和进行夹逼，得到三个数的和。 3Sum Smaller Given an array of n integers nums and a target, find the number of index triplets i, j, k with 0 = target){ ...

tomato 2019-08-14 12:35 评论0 收藏0
3Sum Smaller

摘要：题目链接，从小到大排序固定第一个数字，从后面的数字里选第二个第三个后两个数字，用来找，从开始因为所有之间的数和组合都 3Sum Smaller 题目链接：https://leetcode.com/problems... sort，从小到大排序固定第一个数字index = i，从后面的数字里选第二个第三个后两个数字，用2 points来找，从j = i + 1, k = len(...

Salamander 2019-08-14 17:19 评论0 收藏0
[LintCode/LeetCode] 3Sum Closest

摘要：这个题和的做法基本一样，只要在循环内计算和最接近的和，并赋值更新返回值即可。 Problem Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three intege...

ShevaKuilin 2019-08-14 15:42 评论0 收藏0
[LintCode/LeetCode] 3Sum

摘要：双指针法的解法。然后用和夹逼找到使三数和为零的三数数列，放入结果数组。对于这三个数，如果循环的下一个数值和当前数值相等，就跳过以避免中有相同的解。 Problem Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplet...

Sunxb 2019-08-14 15:42 评论0 收藏0
[LintCode] Count of Smaller Number ［二分法的活用］

摘要：由于这道题目不是查找而是选择第一个的数的位置，所以语句里面可以把和归为同一个分支，因为存在包含重复数的情况，所以要和一样，指针前移替换。那么另一个分支，除了将后移，还要更新返回值。约束条件为的两种写法 Problem Give you an integer array (index from 0 to n-1, where n is the size of this array, va...

2json 2019-08-14 15:16 评论0 收藏0