Added solution for week03 problems

week03/13-Roman-to-Integer.cpp

@@ -0,0 +1,28 @@
+class Solution {
+public:
+    int romanToInt(string str) {
+
+        unordered_map<char, int> roman;
+        roman['I'] = 1;
+        roman['V'] = 5;
+        roman['X'] = 10;
+        roman['L'] = 50;
+        roman['C'] = 100;
+        roman['D'] = 500;
+        roman['M'] = 1000;
+
+        int res = 0, i;
+
+        for ( i = 0 ; i < str.length() - 1; i++){
+            if(roman[str[i]] < roman[str[i+1]]){
+                res -= roman[str[i]];
+            }
+            else{
+                res += roman[str[i]];
+            }
+        }
+        res += roman[str[i]];
+
+        return res;
+    }
+};

week03/146-LRU-Cache.cpp

@@ -0,0 +1,43 @@
+class LRUCache {
+public:
+    int max_cap;
+    list<int>lru;
+    unordered_map<int, int> kv;
+    unordered_map<int, list<int>::iterator> key_address;
+
+    LRUCache(int capacity) {
+        max_cap = capacity;
+    }
+
+    int get(int key) {
+        if(kv.count(key) == 0) {
+            return -1;
+        }
+        updateLRU(key);
+        return kv[key];
+    }
+
+    void put(int key, int value) {
+        if(kv.size() == max_cap && kv.count(key) == 0){
+            evict();
+        }
+        updateLRU(key);
+        kv[key] = value;
+
+    }
+
+    void updateLRU(int key){
+        if(kv.count(key)) {
+            lru.erase(key_address[key]);
+        }
+        lru.push_front(key);
+        key_address[key] = lru.begin();
+
+    }
+
+    void evict() {
+        kv.erase(lru.back());
+        key_address.erase(lru.back());
+        lru.pop_back();
+    }
+};

week03/205-Isomorphic-String.cpp

@@ -0,0 +1,36 @@
+
+// Way - 01
+class Solution {
+public:
+    bool isIsomorphic(string s, string t, int iteration_count = 0) {
+        unordered_map<char, char> from;
+
+        for(int i = 0; i < s.size(); i++){
+            if (from.count(s[i]) && from[s[i]] != t[i] ) {
+                return false;
+            }
+            from[s[i]] = t[i];
+        }
+        if (iteration_count == 0) return isIsomorphic(t, s, 1);
+        return true;
+    }
+};
+
+// Way - 02
+
+class Solution {
+public:
+    bool isIsomorphic(string s, string t) {
+        unordered_map<char, char> from, to;
+
+        for(int i = 0; i < s.size(); i++){
+            if ((from.count(s[i]) && from[s[i]] != t[i] ) || (to.count(t[i]) && to[t[i]] != s[i] )) {
+                return false;
+            }
+            from[s[i]] = t[i];
+            to[t[i]] = s[i];
+        }
+        return true;
+    }
+};
+

week03/2103-Detect-Square.cpp

@@ -0,0 +1,31 @@
+class DetectSquares {
+public:
+    map<pair<int, int>, int> points;
+    DetectSquares() {
+        points.clear();
+    }
+
+    void add(vector<int> point) {
+        int x = point[0];
+        int y = point[1];
+        points[{x, y}]++;
+    }
+
+    int count(vector<int> qpoint) {
+        int total = 0;
+
+        for( auto point : points) {
+            int x1 = point.first.first;
+            int y1 = point.first.second;
+            int x4 = qpoint[0];
+            int y4 = qpoint[1];
+
+            if((x1 == x4) || (abs(x4 - x1) != abs(y4 - y1))) continue;
+
+            if(points.count({x1, y4}) && points.count({x4, y1})){
+                total += (points[{x1, y4}] * points[{x4, y1}] * point.second);
+            }
+        }
+        return total;
+    }
+};