Day-8 Leetcode Coding Journey: Mastering Problem-Solving Techniques

LeetCode #59: Spiral Matrix II

Problem Statement

Given a positive integer n, generate an n x n matrix filled with elements from 1 to n^2 in spiral order.

Constraints

• 1≤n≤20

🚀 Code Implementation

class Solution(object):
    def generateMatrix(self, n):
        """
        :type n: int
        :rtype: List[List[int]]
        """
        matrix=[]
        for i in range(n):
            row=[0]*n 
            matrix.append(row)
        left,right,top,bottom=0,n-1,0,n-1
        num=1
        while left<=right and top<=bottom:
            for i in range(left,right+1):
                matrix[top][i]=num
                num+=1
            top+=1          
            for i in range(top,bottom+1):
                matrix[i][right]=num
                num+=1
            right-=1
            if top<=bottom:
                for i in range(right,left-1,-1):
                    matrix[bottom][i]=num
                    num+=1
                bottom-=1
            if left<=right:
                for i in range(bottom,top-1,-1):
                    matrix[i][left]=num
                    num+=1
                left+=1   
        return matrix

LeetCode #62: Unique Paths

Problem Statement

A robot is located at the top-left corner of an m x n grid.
The robot can only move right or down at any point in time.
The robot must reach the bottom-right corner of the grid.
Find the number of unique paths the robot can take to reach its destination.

Constraints

• 1≤m,n≤100

🚀 Code Implementation

class Solution(object):
    def uniquePaths(self, m, n):
        """
        :type m: int
        :type n: int
        :rtype: int
        """
        dp=[] 
        for i in range(m): 
            row=[1]*n 
            dp.append(row)
        for i in range(1,m):
            for j in range(1,n):
                dp[i][j]=dp[i-1][j]+dp[i][j-1]
        return dp[m-1][n-1]