all i have done till this day

Increasing_Array.cpp

@@ -0,0 +1,19 @@
+#include <iostream>
+using namespace std;
+
+int main() {
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+    int t;
+    cin >> t;
+    unsigned long long int sum=0;
+    int i=0;
+    while (t--) {
+        int j;
+        cin>>j;
+        if(j<i)sum+=i-j;
+        else i=j;
+    }
+    cout<<sum;
+    return 0;
+}

Permutations.cpp

@@ -0,0 +1,27 @@
+#include <iostream>
+using namespace std;
+
+int main() {
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+    int t;
+    cin >> t;
+    if(t==1){
+        cout<<1;
+        return 0;
+    }
+    if(t<4){
+        cout<<"NO SOLUTION";
+        return 0;
+    }
+    int i=2;
+    while(i<=t){
+        cout<<i<<' ';
+        i+=2;
+    }i=1;
+    while(i<=t){
+        cout<<i<<' ';
+        i+=2;
+    }
+    return 0;
+}

Repetitions.cpp

@@ -0,0 +1,27 @@
+#include <iostream>
+using namespace std;
+
+int main() {
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+    int t=1;
+    string s;
+    cin>>s;
+    char prev='#';
+    int count=0;
+    for(char a:s){
+        if(prev=='#'){
+            prev=a;
+            count++;
+            continue;
+        }if(prev==a){
+            count++;
+        }else{
+            prev=a;
+            t=max(count,t);
+            count=1;
+        }
+    }
+    cout<<max(count,t);
+    return 0;
+}

apartments.cpp

@@ -0,0 +1,37 @@
+#include <bits/stdc++.h>
+using namespace std;
+int main() {
+    int n, m, k;
+    std::cin >> n >> m >> k;
+    std::vector<int> applicants(n);
+    std::vector<int> apartments(m);
+
+    for (int i = 0; i < n; ++i) {
+        std::cin >> applicants[i];
+    }
+
+    for (int i = 0; i < m; ++i) {
+        std::cin >> apartments[i];
+    }
+
+    std::sort(applicants.begin(), applicants.end());
+    std::sort(apartments.begin(), apartments.end());
+
+    int i = 0, j = 0, matches = 0;
+    for(int i=0;i<n;i++){
+        while (j < m) {
+            if (std::abs(applicants[i] - apartments[j]) <= k) {
+                ++matches;
+                ++j;
+                break;
+            } else if (apartments[j] < applicants[i] - k) {
+                ++j;
+            }else{
+                break;
+            }
+        }
+    }
+    std::cout << matches << std::endl;
+
+    return 0;
+}

apple_division.cpp

@@ -0,0 +1,33 @@
+#include <climits>
+#include <iostream>
+#include <vector>
+#include <cmath>
+#include <algorithm>
+
+using namespace std;
+
+int main() {
+    int n;
+    cin >> n;
+
+    long long sum = 0;
+    vector<int> weights(n);
+    for (int i = 0; i < n; ++i) {
+        cin >> weights[i];
+        sum += weights[i];
+    }
+
+    long long mn = LLONG_MAX;
+    for (int i = 0; i < (1 << n); i++) {
+        long long sem = 0;
+        for (int k = 0; k < n; k++) {
+            if (1 & (i >> k)) {
+                sem += weights[k];
+            }
+        }
+        mn = min(mn, abs(sum - 2 * sem));
+    }
+
+    cout << mn << endl;
+    return 0;
+}

bit_strings.cpp

@@ -0,0 +1,18 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+int main() {
+    int n;
+    cin >> n;
+    int t=n/28;
+    int p=n%28;
+    unsigned long long int k=1;
+    while(t--){
+        k=(k*(1ULL<<(28)))%1000000007;
+    }
+    if(p){
+         k=(k*(1ULL<<(p)))%1000000007;
+    }
+    cout<<k;
+    return 0;
+}

chessboard_queens.cpp

@@ -0,0 +1,38 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+int placequeen(vector<vector<bool>>& vim, int queen) {
+    if (queen == 8) {
+        return 1;
+    }
+    int count = 0;
+    for (int j = 0; j < 8; j++) {
+        if (!vim[queen][j]) {
+            vector<vector<bool>> vp = vim;
+            for (int x = 0; x < 8; x++) {
+                for (int y = 0; y < 8; y++) {
+                    if (x == queen || y == j || abs(x - queen) == abs(y - j)) { 
+                        vp[x][y] = 1;
+                    }
+                }
+            }
+            count += placequeen(vp, queen + 1);
+        }
+    }
+    return count;
+}
+
+int main() {
+    vector<vector<bool>> vim(8, vector<bool>(8, 0));
+    for (int i = 0; i < 8; i++) {
+        for (int j = 0; j < 8; j++) {
+            char p;
+            cin >> p;
+            if (p == '*') {
+                vim[i][j] = 1;
+            }
+        }
+    }
+    cout << placequeen(vim, 0);
+    return 0;
+}

coin_piles.cpp

@@ -0,0 +1,24 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+int main() {
+    int t;
+    cin >> t;
+
+    while (t--) {
+        int a, b;
+        cin >> a >> b;
+
+        // Ensure a >= b for simplicity
+        if (a < b) swap(a, b);
+
+        // Check if the piles can be emptied
+        if ((a + b) % 3 == 0 && a <= 2 * b) {
+            cout << "YES\n";
+        } else {
+            cout << "NO\n";
+        }
+    }
+
+    return 0;
+}

concert_tickets.cpp

@@ -0,0 +1,30 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+int main() {
+    multiset<int> tickets;
+    int n, m;
+    cin >> n >> m;
+
+    for (int i = 0; i < n; i++) {
+        int t;
+        cin >> t;
+        tickets.insert(t);
+    }
+
+    for (int i = 0; i < m; i++) {
+        int t;
+        cin >> t;
+        auto it = tickets.upper_bound(t);
+
+        if (tickets.empty() || it == tickets.begin()) {
+            cout << -1 << endl;
+        } else {
+            --it;
+            cout << *it << endl;
+            tickets.erase(it); 
+        }
+    }
+
+    return 0;
+}

creating_strings.cpp

@@ -0,0 +1,39 @@
+#include <bits/stdc++.h>
+#include <string>
+using namespace std;
+void recursion(string& t , set<string>& s,int n){
+    if(s.find(t)!=s.end()){
+        return;
+    }
+    s.insert(t);
+    for(int i=0;i<n;i++){
+        for(int j=i+1;j<n;j++){
+            string p=t;
+            swap(p[i],p[j]);
+            recursion(p, s, n);
+        }
+    }
+}
+int main() {
+    string t;
+    cin>>t;
+    sort(t.begin(),t.end());
+    int n=t.size();
+    vector<int> alpa(26 ,0);
+    for(char c:t){
+        alpa[c-'a']++;
+    }
+    int k=tgamma(n+1);
+    for(auto a:alpa){
+        if(a>1){
+            k=k/tgamma(a+1);
+        }
+    }
+    cout<<k<<endl;
+    set<string> s;
+    recursion(t, s, n);
+    for(string p:s){
+        cout<<p<<endl;
+    }
+    return 0;
+}

digit_queries.cpp

@@ -0,0 +1,28 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+int main() {
+    int t;
+    cin >> t;
+    while (t--) {
+        long long x;
+        cin >> x;
+
+        long long less = 9;
+        int count = 1;
+        while (x > less * count) {
+            x -= less * count;
+            less *= 10;
+            count++;
+        }
+        long long quo = (x - 1) / count;
+        int remain = (x - 1) % count;
+
+        long long number = less / 9 + quo;
+
+        string s = to_string(number);
+        cout << s[remain] << endl;
+    }
+
+    return 0;
+}

distinct_numbers.cpp

@@ -0,0 +1,17 @@
+#include <bits/stdc++.h>
+using namespace std;
+int main() {
+    int t;
+    cin>>t;
+    int co=0;
+    set<int> s;
+    while(t--){
+        int x;
+        cin>>x;
+        if(s.find(x)==s.end()){
+        s.insert(x);
+        co++;
+        }
+    }cout<<co;
+    return 0;
+}

ferris_wheel.cpp

@@ -0,0 +1,27 @@
+#include <bits/stdc++.h>
+using namespace std;
+int main() {
+    int n, x;
+    std::cin >> n >> x;
+    multiset<int> s;
+    for(int i=0;i<n;i++){
+        int k;
+        cin>>k;
+        s.insert(k);
+    }
+    int co=0;
+    while(!s.empty()){
+        co++;
+        auto it=s.begin();
+        int p=*it;
+        s.erase(it);
+        it=s.upper_bound(x-p);
+        if(it!=s.begin()){
+            it--;
+            s.erase(it);
+        }
+
+    }
+    cout<<co;
+    return 0;
+}