leetcode13

Spiral Matrix

#coding=utf-8

class Solution(object):
    def spiralOrder(self, matrix):
        """
        :type matrix: List[List[int]]
        :rtype: List[int]
        """
        res=[]
        while matrix:
            if len(matrix)==0:
                break
            for i in matrix[0]:
                res.append(i)
            matrix.pop(0)
            if len(matrix)==0:
                break
            for i in range(len(matrix)):
                res.append(matrix[i][-1])
                matrix[i].pop()
            if len(matrix[0])==0:
                break
            for i in matrix[-1][::-1]:
                res.append(i)
            matrix.pop()
            if len(matrix)==0:
                break
            for i in range(len(matrix)-1,-1,-1):
                res.append(matrix[i][0])
                matrix[i].pop(0)
            if len(matrix[0])==0:
                break
        return res

Sudoku Solver
牛客上做过一遍,结果忘了。。。

class Solution(object):
    def solveSudoku(self, board):
        """
        :type board: List[List[str]]
        :rtype: void Do not return anything, modify board in-place instead.
        """
        def isValid(x,y):
            temp=board[x][y]
            board[x][y]='D'
            for i in range(9):
                if board[i][y]==temp:
                    return False
            for i in range(9):
                if board[x][i]==temp:
                    return False
            for i in range(3):
                for j in range(3):
                    if board[x/3*3+i][y/3*3+j]==temp:
                        return False
            board[x][y]=temp
            return True

        def dfs(board):
            for i in range(9):
                for j in range(9):
                    if board[i][j]=='.':
                        for k in '123456789':
                            board[i][j]=k
                            if isValid(i,j) and dfs(board):
                                return True
                            board[i][j]='.'
                        return False
            return True
        dfs(board)

Jump Game
自己用动态规划,结果超时了,这O(n)的方法真强。。。

class Solution:
    # @param A, a list of integers
    # @return a boolean
    def canJump(self, A):
        step = A[0]
        for i in range(1, len(A)):
            if step > 0:
                step -= 1
                step = max(step, A[i])
            else:
                return False
        return True

Count Primes
使用埃拉托斯特尼筛法

class Solution(object):
    def countPrimes(self, n):
        """
        :type n: int
        :rtype: int
        """
        n=max(n,2)
        isPrime=[True for i in range(n)]
        isPrime[0],isPrime[1]=False,False
        temp=2
        while temp**2if isPrime[temp]:
                p=temp**2
                while pFalse
                    p+=temp
            temp+=1
        count=0
        for i in range(n):
            if isPrime[i]==True:
                count+=1
        return count

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