Add solutions for problems 3, 13, 125, and 680

Author: DarkSnakeX

src/main/java/me/darksnakex/problems/p125.java

@@ -0,0 +1,22 @@
+package me.darksnakex.problems;
+
+public class p125 {
+
+    public boolean isPalindrome(String s) {
+
+        String res = s.toLowerCase().replaceAll("[^a-z0-9]", "");
+
+        int der = res.length() - 1;
+        for (int izq = 0; izq < res.length() / 2; izq++) {
+            // Caso de letras no iguales
+            if (res.charAt(der) != res.charAt(izq)) {
+                return false;
+            }
+            der--;
+
+        }
+
+        return true;
+    }
+
+}

src/main/java/me/darksnakex/problems/p13.java

@@ -0,0 +1,39 @@
+package me.darksnakex.problems;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class p13 {
+
+    public int romanToInt(String s) {
+
+        int res = 0;
+
+        Map<Character,Integer> map =  new HashMap<>();
+        map.put('I',1);
+        map.put('V',5);
+        map.put('X',10);
+        map.put('L',50);
+        map.put('C',100);
+        map.put('D',500);
+        map.put('M',1000);
+
+        char actual;
+        for(int i = 0; i <s.length()-1; i++){
+            actual = s.charAt(i);
+            if(map.get(actual) >= map.get(s.charAt(i+1)) ){
+                res+=map.get(actual);
+            }
+            else{
+                res-=map.get(actual);
+            }
+        }
+
+
+        return res + map.get(s.charAt(s.length() - 1));
+
+
+
+    }
+
+}

src/main/java/me/darksnakex/problems/p3.java

@@ -0,0 +1,33 @@
+package me.darksnakex.problems;
+
+public class p3 {
+
+    public int lengthOfLongestSubstring(String s) {
+
+        StringBuilder res = new StringBuilder();
+        int cont = 0;
+        int fin = 0;
+
+        for (int i = 0; i < s.length(); i++) {
+            String ac = String.valueOf(s.charAt(i));
+            //System.out.println(ac);
+            if (!(res.toString().contains(ac))) {
+                res.append(ac);
+                cont++;
+
+            } else {
+
+                fin = Math.max(fin, cont);
+                int indice = res.indexOf(ac);
+                if (indice != -1) {
+                    res = new StringBuilder(res.substring(indice + 1)).append(ac);
+                    cont = res.length();
+                }
+
+            }
+
+        }
+        return Math.max(fin, cont);
+
+    }
+}

src/main/java/me/darksnakex/problems/p680.java

@@ -0,0 +1,39 @@
+package me.darksnakex.problems;
+
+public class p680 {
+
+
+    public boolean validPalindrome(String s) {
+
+        StringBuilder res = new StringBuilder(s);
+
+        int der = res.length()-1;
+        for(int izq = 0; izq < res.length()/2; izq++){
+            // Caso de letras no iguales
+            if(res.charAt(der) != res.charAt(izq)){
+                StringBuilder res2 = new StringBuilder(res);
+                return aux(res.deleteCharAt(izq), izq, der) || aux(res2.deleteCharAt(der), izq, der);
+            }
+            der--;
+
+        }
+
+        return true;
+    }
+
+    private boolean aux(StringBuilder text, int izq, int der){
+        der--;
+        for(; izq < text.length()/2; izq++){
+            // Caso de letras no iguales
+            if(text.charAt(der) != text.charAt(izq)){
+                return false;
+            }
+            der--;
+
+        }
+
+        return true;
+
+    }
+
+}