Pretty Sure

LeetCode - Valid Triangle Number

Question Definition

Given an array consists of non-negative integers, your task is to count the number of triplets chosen from the array that can make triangles if we take them as side lengths of a triangle. Example 1:

Input: [2,2,3,4]
Output: 3
Explanation:
Valid combinations are:
2,3,4 (using the first 2)
2,3,4 (using the second 2)
2,2,3

Note:

1. The length of the given array won’t exceed 1000.
2. The integers in the given array are in the range of [0, 1000].

   My Java Solution

   public int triangleNumber(int[] nums) {
    Arrays.sort(nums);
    int result = 0;
    for(int i = 0; i < nums.length; i++){
        for(int j = i + 1; j < nums.length; j++){
            for(int k = j + 1; k < nums.length; k++){
                if(nums[i] + nums[j] > nums[k])
                    result++;
            }
        }
    }
    return result;
   }
   

   Best Java Solution

   public int triangleNumber(int[] nums) {
    int res = 0, n = nums.length;
    Arrays.sort(nums);
    for (int i = n - 1; i >= 2; --i) {
        int left = 0, right = i - 1;
        while (left < right) {
            if (nums[left] + nums[right] > nums[i]) {
                res += right - left;
                --right;
            } else {
                ++left;
            }
        }
    }
    return res;
   }
   

LeetCode -

Question Definition

A robot is located at the top-left corner of a m x n grid (marked ‘Start’ in the diagram below).

The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked ‘Finish’ in the diagram below).

How many possible unique paths are there?

LeetCode - Task Scheduler

Question Definition

Given a char array representing tasks CPU need to do. It contains capital letters A to Z where different letters represent different tasks.Tasks could be done without original order. Each task could be done in one interval. For each interval, CPU could finish one task or just be idle.

However, there is a non-negative cooling interval n that means between two same tasks, there must be at least n intervals that CPU are doing different tasks or just be idle.

You need to return the least number of intervals the CPU will take to finish all the given tasks.

LeetCode - Subsets

Question Definition

Given a set of distinct integers, nums, return all possible subsets (the power set).

**Note: **The solution set must not contain duplicate subsets.

LeetCode - Spiral Matrix II

Question Definition

Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.