Codeforces Round 603 (Div. 2) Broken Editorial

Introduction

First time writing a Codeforces contest review in English

I have been participating in the Codeforces rounds since this October.

A. Sweet Problem

Problem Link

I thought this problem is easy to solve since its scoring is 500.

It was tough to find a way to think of how to find the maximum day.

My algorithm to find the max day :

1.Sort the input numbers.

2.If the smallest number, arr[0], is smaller than the difference between arr[1] and arr[2], the answer is arr[0] + arr[1].

3.Otherwise, some of arr[0] is used to make arr[1] and arr[2] equal and then the rest of arr[0] is evenly eaten wtih arr[1] and arr[2].

Be careful! If the rest of arr[0] is odd, the answer should be lessened by 1.

#include <cstdio>
#include <algorithm>
using namespace std;
long long k, arr[3];
int main(){
    scanf("%lld", &k);
    while(k--){
        scanf("%lld %lld %lld", &arr[0], &arr[1], &arr[2]);
        long long ans = 0;
        sort(arr, arr + 3);
        int dif = arr[2] - arr[1];
        if(dif >= arr[0])ans = arr[0] + arr[1];
        else{
            if((arr[0] - dif) % 2 == 0)ans = arr[0] + arr[1] - (arr[0] - dif) / 2;
            else ans = arr[0] + arr[1] - (arr[0] - dif) / 2 - 1;
        }     
        printf("%lld\n", ans);
    }
}

B. PIN Codes

Problem Link

This problem can be seen hard if you don’t see the condition that n is 10.

I just receive numbers and put them in the array.

Array cnt is used to see the number is duplicated or not.

To change digits of the number, I use 3 variables, x for thousands, y for hundreds and z for ones.

If a number is duplicated, it looks for a valid number using x, y, z.

Then, finally put the number into the answer.

#include <algorithm>
#include <cstring>
#include <cstdio>
#include <vector>
using namespace std;
int n, t, temp, num[11], cnt[10001];
int main(){
    scanf("%d", &t);
    while(t--){
        int ans = 0;
        vector<int> nums;
        scanf("%d", &n);
        memset(cnt, 0, sizeof(cnt));
        for(int i = 0; i < n; i++){
            scanf("%d", &num[i]);
            cnt[num[i]]++;
        }
        for(int i = 0; i < n; i++){
            if(cnt[num[i]] == 1){
                nums.push_back(num[i]);
                continue;
            }
            ans ++;
            int x = num[i] % 1000, y = num[i] - x / 100 * 100, z = num[i] - num[i] % 10;
            for(int j = 0; j < 10; j++){
                int temp[3];
                temp[0] = x + j * 1000, temp[1] = y + j * 100, temp[2] = z + j;
                for(int k = 0; k < 3; k++){
                    if(!cnt[temp[k]]){
                        cnt[temp[k]] ++;
                        nums.push_back(temp[k]);
                        break;
                    }
                }
            }
            cnt[num[i]]--;
        }
        printf("%d\n", ans);
        for(int i = 0; i < n; i++){
            if(nums[i] / 10 == 0)printf("000");
            else if(nums[i] / 100 == 0)printf("00");
            else if(nums[i] / 1000 == 0)printf("0");
            printf("%d\n", nums[i]);
        }

    }
}

C. Everyone is a Winner!

Problem Link

This problem is easy if you find out a way to find numbers.

If the number is 11, starting from 1 to the square root of 11, you will find the result of the divison.

you simply add divisor and quotient to the answer vector.

#include <algorithm>
#include <vector>
#include <cstdio>
#include <cmath>
using namespace std;
long long n, m, t;
int main(){
    scanf("%lld", &t);
    while(t--){
        scanf("%lld", &n);
        vector<long long> ans;
        long long prev = 0, p = sqrt(n);
        for(long long i = 1; i <= p; i++){
            ans.push_back(i); 
            if(i != n / i)ans.push_back(n / i);
        }
        sort(ans.begin(), ans.end());
        printf("%lu\n0 ", ans.size() + 1);
        for(long long i = 0; i < ans.size(); i++)printf("%lld ", ans[i]);
        printf("\n");
    }
}

D. Secret Passwords

Problem Link

I had only 20 mins to solve this problem.

The goal is to find the minimum number of passwords that can cover all of the list.

This can be solved by finding letter sets that can cover more pw in the list.

If a password is with more than one letter, union the letters in it.

Then, count the numbers of disjoint letter sets.

#include <cstdio>
char s[51];
int ans, n, m, t, par[26], visited[26];
int find(int x) {
    if (x == par[x])return x;
    return par[x] = find(par[x]);
}
int main(){
    scanf("%d", &n);
    for(int i = 0; i < 26; i++)par[i] = i;
    for(int i = 0; i < n; i++){
        scanf("%s", s);
        for(int j = 0; s[j] != '\0'; j++){
            visited[s[j] - 'a'] = 1;
            if(s[j + 1] == '\0')break;
            int p1 = find(s[j] - 'a'), p2 = find(s[j + 1] - 'a');
            if(p1 == p2)continue;
            else par[p1] = p2;
        }
    }
    for(int i = 0; i < 26; i++){
        if(visited[i] == 0)continue;
        if(par[i] == i)ans++;
    }
    printf("%d", ans);
}

If you find better ways to solve in my code or have any questions, leave a comment!

Introduction
A. Sweet Problem
B. PIN Codes
C. Everyone is a Winner!
D. Secret Passwords