string qs easy.

Author: JanaSabuj

Top Qs/Strings/Count and Say.cpp

@@ -0,0 +1,39 @@
+class Solution {
+public:
+    string countAndSay(int n) {
+        vector<string> ans(n + 1);
+        
+        ans[1] = "1";
+        if(n == 1)
+            return "1";
+   
+        for(int i = 2; i <= n; i++){
+            string prev = ans[i-1];
+            
+            int l = 0;
+            int r = 0;
+            string temp = "";
+            int x = prev.size();
+            cout << x << endl;
+            
+            while(r < x){
+                if(prev[r] == prev[l])
+                    r++;
+                else{
+                    temp += to_string(r-l);
+                    temp += to_string(prev[l] - '0');
+                    l = r;
+                }
+                    
+            }
+            
+            temp += to_string(r-l);
+            temp += to_string(prev[l] - '0');
+            
+            ans[i] = temp;
+            
+        }
+        
+        return ans[n];
+    }
+};

Top Qs/Strings/First Unique Character In a String.cpp

@@ -0,0 +1,15 @@
+class Solution {
+public:
+    int firstUniqChar(string s) {
+        map<int,int> mp;
+        for(auto c: s)
+            mp[c]++;
+        
+        int n = s.length();
+        for(int i = 0; i < n; i++)
+            if(mp[s[i]] == 1)
+                return i;
+        
+        return -1;
+    }
+};

Top Qs/Strings/LCP.cpp

@@ -0,0 +1,30 @@
+class Solution {
+public:
+    
+    string LCP(string a, string b){
+        int i = 0, j = 0;
+        while(i < (int)a.length() and j < (int)b.length()){
+            if(a[i] == b[j]){
+                i++;
+                j++;
+            }else{
+                return a.substr(0, i);                
+            }
+        }
+        
+        return a.substr(0, i);
+         
+    }
+    
+    string longestCommonPrefix(vector<string>& strs) {
+        int n = strs.size();
+        if(n == 0)
+            return "";
+        
+        string ans = strs[0];
+        for(auto str: strs){
+            ans = LCP(ans, str);
+        }
+        return ans;
+    }
+};

Top Qs/Strings/Reverse Integer.cpp

@@ -0,0 +1,18 @@
+class Solution {
+public:
+    int reverse(int x) {
+        long long ans = 0;
+        
+        while(x){
+           
+            ans = ans * 10 + x % 10;
+            x = x/10;
+            
+         if(ans > INT_MAX or ans < INT_MIN)
+                return 0;
+            
+        }
+        
+        return  ans;
+    }
+};

Top Qs/Strings/Reverse String.cpp

@@ -0,0 +1,16 @@
+class Solution {
+public:
+    void reverseString(vector<char>& s) {
+        int n = s.size();
+        int i = 0, j = n-1;
+        
+        while(i < j){
+            swap(s[i], s[j]);
+            i++;
+            j--;
+        }
+        
+        
+        
+    }
+};

Top Qs/Strings/Stribg to integer(atoi).cpp

@@ -0,0 +1,45 @@
+class Solution {
+public:
+    int myAtoi(string str) {
+        int n = str.length();
+        int i = 0;
+        bool neg = false;
+        while(str[i] == ' ')
+            i++;
+        
+        if(str[i] == '-'){
+            neg = true;
+            i++;
+        }
+        else if(str[i] == '+'){
+            neg = false;
+            i++;
+        }
+        
+        if(!isdigit(str[i]))
+            return 0;
+        
+        long long ans = 0;
+        while(i < n){
+            if(!isdigit(str[i]))
+                break;
+            ans = ans * 10 + str[i] - '0';
+            i++;
+          
+            ans = (neg ? -ans : ans);
+             if(ans < INT_MIN)
+                 return INT_MIN;
+              if(ans > INT_MAX)
+                 return INT_MAX;
+            
+            ans = abs(ans);
+        }
+        
+         ans = (neg ? -ans : ans);
+        
+        
+        return ans;
+        
+        
+    }
+};

Top Qs/Strings/Valid Anagram.cpp

@@ -0,0 +1,15 @@
+class Solution {
+public:
+    bool isAnagram(string s, string t) {
+        map<int,int> mp;
+        for(auto c: s)
+            mp[c]++;
+        for(auto c: t)
+            mp[c]--;
+        
+        for(auto x: mp)
+            if(x.second != 0)
+                return false;
+        return true;
+    }
+};

Top Qs/Strings/Valid Palindrome.cpp

@@ -0,0 +1,28 @@
+class Solution {
+public:
+    bool isPalindrome(string s) {
+        int n = s.length();
+        if(n == 0 or n == 1)
+            return true;
+        
+        int i = 0, j = n-1;
+        while(i < j){
+            if(!isalnum(s[i])){
+                i++;
+                continue;
+            }
+            if(!isalnum(s[j])){
+                j--;
+                continue;
+            }
+           
+                if(tolower(s[i]) != tolower(s[j]))
+                    return false;
+                i++;
+                j--;                            
+               
+        }
+        
+        return true;
+    }
+};

Top Qs/Strings/implement strStr().cpp

@@ -0,0 +1,24 @@
+class Solution {
+public:
+    int strStr(string haystack, string needle) {
+        int k = needle.size();
+        if(k == 0)
+            return 0;
+        for(int i = 0; i <= (int)haystack.size() - (int)needle.size(); i++){
+            bool found = true;
+            
+            for(int j = 0; j < (int)needle.size(); j++){
+                if(haystack[i+j] != needle[j]){
+                    found = false;
+                    break;
+                }                    
+            }
+            
+            if(found)
+                return i;
+            
+        }
+        
+        return -1;
+    }
+};