【面試題13】機器人的運動範圍

Python題解
這題和12題思路一樣，都是回溯法的使用。

class Solution:
    def movingCount(self, threshold, rows, cols):
        if threshold < 0 or rows < 0 or cols < 0: return 0
        visited = [False] * (rows * cols)
        def getDigitSum(num):
            count_sum = 0
            while num != 0:
                count_sum += num % 10
                num = num // 10
            return count_sum
        def check(rows, cols, row, col, threshold, visited):
            if row >=0 and row < rows and col >= 0 and col < cols \
                and getDigitSum(row)+getDigitSum(col) <= threshold\
                and not visited[row*cols+col]:
                return True
            return False
        def helper(rows, cols, row, col, threshold, visited):
            count = 0
            if check(rows, cols, row, col, threshold, visited):
                visited[row*cols+col] = True
                count = 1 + helper(rows, cols, row-1, col, threshold, visited)+ \
                helper(rows, cols, row+1, col, threshold, visited)+ \
                helper(rows, cols, row, col-1, threshold, visited)+ \
                helper(rows, cols, row, col+1, threshold, visited)
            return count
        res = helper(rows, cols, 0, 0, threshold, visited)
        return res

考點

• 考查對回溯法的理解。通常物體或人在二維方格運動這類問題都可以用回溯法解決。
• 考查對數組編程的能力。一般把矩陣看成一個二維的數組，只有對數組的特性充分了解，纔可能快速、正確實現對回溯代碼編寫。