Niuke real problem programming - day18

Compile environment ：c++

1、 Expression legal judgment

describe ：

Write a piece of code , Judge one including '{','[','(',')',']','}' Whether the expression of is legal ( Pay attention to the legal rules in the sample .)

You can see a legal expression , The left and right parentheses must correspond to each other .

Given an expression A, Please return one bool value , Represents whether it is legal .

Algorithmic thought ：

The title does not give a clear description , You can pass the test without considering the order of the left and right parentheses , Therefore, you only need to judge whether the number of left and right parentheses matches , Left bracket self addition 1, The right bracket is subtracted , If the last count is 0, Then it's legal .

The code part implements ：

2、 Remove duplicate characters

describe ：

Niuniu has a string of lowercase letters s, stay s There may be some repeated letters in . For example "banana" in , Letter 'a' And letters 'n' Three times and two times respectively .
But Niuniu doesn't like repetition . For the same letter , He just wants to keep the first appearance and delete the following letters . Please help Niuniu finish the right s The operation of .

Algorithmic thought ：

Using character conversion ascii Code for the number of times each letter appears , When count is 0 when , Output the string element that appears for the first time .

3、 Fort attack

describe

After Rambo taught Timo , Then discuss the Yodel people with Timo , Talking about the Yodel people , Naturally, there is no shortage of one person , that It's heimerdinger ------ The greatest scientist in the history of the Yodel people . Timo said , Heimodinger has been thinking about a problem recently : Heimerdinger has three forts , The fort can attack at a distance of less than or equal to R The enemy of ( The distance between two points is the linear distance between two points , for example (3,0),(0,4) The distance between them is 5), If a fort can attack To the enemy , Then it will cause 1× The damage of . Heimerdinger put three forts on N*M On the dot in the square , And give the enemy Coordinates of . ask : How much damage will the enemy suffer ?

Algorithmic thought ：

The topic has multiple sets of use case input , For each use case input , Record the point coordinates of the corresponding fort and the enemy , Calculate the distance between two points respectively and compare with the range of the fort .

The code part implements ：