C++ STL: algorithms problems

Problems:

• Here is the list of questions to practice STL algorithms:
• 1. UVa 00123 - Searching Quickly
• 2. UVa 00146 - ID Codes *
• 3. UVa 00400 - Unix ls
• 4. UVa 00450 - Little Black Book
• 5. UVa 00790 - Head Judge Headache
• 6. UVa 00855 - Lunch in Grid City
• 7. UVa 01209 - Wordfish
• UVa 10057 - A mid-summer night ... 
• UVa 10107 - What is the Median? * 
• UVa 10194 - Football a.k.a. Soccer
• UVa 10258 - Contest Scoreboard *
• UVa 10698 - Football Sort
• UVa 10880 - Colin and Ryan
• UVa 10905 - Children’s Game
• UVa 11039 - Building Designing
• UVa 11321 - Sort Sort and Sort
• UVa 11588 - Image Coding
• UVa 11777 - Automate the Grades
• UVa 11824 - A Minimum Land Price
• UVa 12541 - Birthdates

Here is the link to these questions: https://onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=625

Here are hints and my solutions to some of these:

Hint and Solutions

Uva 00146: ID Codes

Simple: You need to use the next_permutation. Here is my code that solves the problem:

#include <bits/stdc++.h>
	using namespace std;
	int main(int argc, char const *argv[]) {
	string s;
	while (getline(cin, s),s!="#") {
	string t = s;
	sort(t.begin(), t.end());
	next_permutation(s.begin(),s.end());
	if(t==s)
	std::cout << "No Successor" << '\n';
	else
	std::cout <<s<< '\n';
	}
	return 0;
	}

Uva 10107: What is the Median?

Create an array of size 100000, store all elements into it, keeping track of the last filled location. Each time filling a location in it, sort using the sort function it and output the median as defined in the problem.

Here is the code that does it:

#include <bits/stdc++.h>
	using namespace std;
	int main(int argc, char const *argv[]) {
	int arr[100003];
	int end=0;
	int temp;
	while (scanf("%d", &temp)==1) {
	end;
	arr[end] = temp;
	sort(arr, arr+end+1);
	int median;
	if(end==0)
	median = arr[0];
	else if(end%2==1&&end!=0)
	median = (arr[end/2] + arr[end/2 +1])/2;
	else
	median = arr[end/2];
	end++;
	printf("%d\n", median);
	}
	return 0;
	}

Uva 10905: Children's Game

You need a modified form of the sort function, create a compare function that does the job. Head here to learn it: https://rishabhjainiitbhu.blogspot.com/2019/08/custom-sorting-in-c.html

Here is the code that solves the problem:

#include <bits/stdc++.h>
	using namespace std;
	bool compare(const string &a,const string &b){
	if(a+b>b+a)
	return true;
	else
	return false;
	}
	int main(int argc, char const *argv[]) {
	int N;
	while (scanf("%d", &N), N!=0) {
	string arr[N];
	for (size_t i = 0; i < N; i++) {
	cin>>arr[i];
	}
	sort(arr, arr+N, compare);
	for (size_t i = 0; i < N; i++) {
	cout<<arr[i];
	}
	cout<<'\n';
	}
	return 0;
	}

Uva 11321: Sort! Sort! and Sort!

Create a custom sorting function. Keep in mind the negative numbers.

Here is my solution to the problem:

#include <bits/stdc++.h>
	using namespace std;
	int M;
	bool compare(int a, int b){
	int temp= a%M;
	int temp2= b%M;
	if(temp<temp2)
	return true;
	if(temp>temp2)
	return false;
	if(a%2==0&&b%2==1||(a%2==0&&b%2==-1))
	return false;
	if(a%2==1&&b%2==0||(a%2==-1&&b%2==0))
	return true;
	if((a%2==1||a%2==-1)&&a>b)
	return true;
	if((a%2==1||a%2==-1)&&a<b)
	return false;
	if(a%2==0&&a>b)
	return false;
	if(a%2==0&&a<b)
	return true;
	return false;
	}
	int main(int argc, char const *argv[]) {
	int N;
	while(scanf("%d %d", &N, &M), N||M) {
	int arr[N];
	for (size_t i = 0; i < N; i++) {
	scanf("%d", &arr[i]);
	}
	sort(arr, arr+N, compare);
	printf("%d %d\n", N, M);
	for (size_t i = 0; i < N; i++) {
	printf("%d\n", arr[i]);
	}
	}
	printf("%d %d\n", 0, 0);
	return 0;
	}

Uva 11777: Automate the Grades

No hint(or even the code) should be needed. Still, here is my code:

#include <bits/stdc++.h>
	using namespace std;
	inline int average(int ct1, int ct2, int ct3){
	if(ct1<ct2)swap(ct1, ct2);
	if(ct2<ct3)swap(ct2, ct3);
	return (ct1+ct2)/2;
	}
	int main(int argc, char const *argv[]) {
	int T;
	scanf("%d\n", &T);
	int i=1;
	while(T--){
	int term1, term2, final, attendance, class_test1, class_test2, class_test3;
	scanf("%d %d %d %d %d %d %d\n", &term1, &term2, &final, &attendance, &class_test1, &class_test2, &class_test3);
	int total = term1+term2+final+attendance + average(class_test1, class_test2, class_test3);
	printf("Case %d: ", i++);
	if(total<60){
	printf("%c\n", 'F');
	continue;
	}
	if(total<70){
	printf("%c\n", 'D');
	continue;
	}
	if(total<80){
	printf("%c\n", 'C');
	continue;
	}
	if(total<90){
	printf("%c\n", 'B');
	continue;
	}
	printf("%c\n", 'A');
	}
	return 0;
	}