Huawei Machine Question "1"

Title Description:

The teacher wants to know from the so-and-so classmate, the highest score is how many, now asks you to program the simulation teacher's inquiry. Of course, teachers sometimes need to update a student's grades.

Input Description:

The input includes multiple sets of test data.
The first line of each set of inputs is two positive integers N and m (0 < N <= 30000,0 < M < 5000), representing the number of students and the number of operations respectively.
Student ID number from 1 to N.
The second line contains n integers representing the initial scores of the N students, where the number of I represents the student's score for ID i.
Next M-line, each line has a character C (only ' Q ' or ' U '), and two positive integers, a, B, when C is ' Q ', indicating that this is a query operation, he asked the ID from a to B (including A, a) among students, the highest performance is how much
When C is ' U ', it indicates that this is an update operation that requires the student with ID A to change the grade to B.

Output Description:

For each query operation, output the highest score in one line.

Input Example:

5 7
1 2 3) 4 5
Q 1 5
U 3 6
Q 3 4
Q 4 5
U 4 5
U 2 9
Q 1 5

Output Example:

5
6
5
9

Thinking Analysis:

• Pay attention to multiple sets of test data in the topic, need to loop to determine the input
• One of the Q query, a and B to determine the size of a, and b corresponding to the array index will be reduced by one
• The ontology takes the array and stores the first n numbers, traverses m times, operates, takes the most direct way, the time complexity is O (n), the improved method considers the data structure of the segment tree, modifies O (logn), Queries O (Logn), but to Preprocess O (Nlogn), or a block list (in fact, a block array is OK).
  Quite simply, now we're going to split the entire n-size array into sqrt (n) (square root N) decimal groups with sqrt (n) elements per decimal group
  For example 1 2 3 4 5 6 7 8 9
  Now split into
  1 2 3
  4 5 6
  7 8 9
  Then for each small piece, we have to change the value of the corresponding position, but also to record the maximum value of the entire small block.
  If I update, the maximum value of that small piece increases, it is simple, the maximum value also increases.
  What if the maximum is changed to a smaller number? In order to be correct, we can only sweep the whole small piece and re-calculate the maximum value.
  Therefore, the complexity of the modification is O (sqrt (n))

Sample code (Java)

Import Java.util.Scanner; Public classMain { Public Static void Main(string[] args) {intm=0, n=0;intIintA =0, B =0; Scannerinch=NewScanner (System.inch); while(inch. Hasnext ()) {N =inch. Nextint (); M =inch. Nextint ();//System.out.println (N + "" + M);            int[] score =New int[N]; for(i=0;inch. Hasnext () && i<n; i++) {Score[i] =inch. Nextint ();//System.out.println (Score[i] + "");} String C =NULL; for(i=0;inch. Hasnext () && i< M; i++) {c =inch. Next (); A =inch. Nextint (); B =inch. Nextint ();            Deal (C,a,b,score); }        }    }Private Static void deal(String C,intAintBint[] score) {intBegin,end;if(C.equals ("Q") {end = Math.max (A, b); Begin = Math.min (A, B)-1;intmax = Score[begin]; for(inti=begin;i<end;i++) {if(Max<score[i])                {max = score[i]; }} System. out. println (max); }Else if(C.equals ("U")) {score[a-1] = b; }    }}

Reference:
http://www.nowcoder.com/questionTerminal/3897c2bcc87943ed98d8e0b9e18c4666

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Huawei Machine Question "1"