new algoriths added

Author: jbhattac

ExpressionBalance.java

@@ -0,0 +1,57 @@
+package ds.algo.solutions;
+
+import java.util.Stack;
+
+public class ExpressionBalance {
+	
+	public static void main(String[] args) {
+		System.out.println(isBalanced("{{{([[[]]])()()()}}}"));
+		System.out.println(isBalanced("{{{([[[m+l]]])(x+3)(p-q-w-e-e-e)(f-d-r-e)}}}"));
+		System.out.println(isBalanced("{{{([[[m+l]]])(x+3)(p-q-w-e-e-e)(f-d-r-e)}}}{]"));
+	}
+
+	static String isBalanced(String s) {
+        // Complete this function
+        int b1 = 0, b2 = 0, b3 = 0;
+        char ch;
+        Stack<Character> nextClose = new Stack<>();
+        
+        for (int i = 0; i < s.length(); i++){
+            ch = s.charAt(i);
+            if (ch == '[') {
+                b3++;
+                nextClose.push(']');
+            }
+            else if (ch == ']') {
+                b3--;
+                if (nextClose.isEmpty() || nextClose.pop() != ch) return "NO";
+                if(b3<0) {
+                    return "NO";
+                }
+            }
+            else if (ch == '{') {
+                b2++;
+                nextClose.push('}');
+            }
+            else if (ch == '}') {
+                b2--;
+                if (nextClose.isEmpty() || nextClose.pop() != ch) return "NO";
+                if(b2<0) {
+                    return "NO";
+                }
+            }
+            else if (ch == '(') {
+                b1++;
+                nextClose.push(')');
+            }
+            else if (ch == ')') {
+                b1--;
+                if (nextClose.isEmpty() || nextClose.pop() != ch) return "NO";
+                if(b1<0) {
+                    return "NO";
+                }
+            }
+        }
+        return b1 + b2 + b3 == 0 ? "YES" : "NO";
+    }
+}

RomanConverter.java

@@ -0,0 +1,89 @@
+package ds.algo.solutions;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class RomanConverter {
+
+	public static Map<Integer, String> INTEGER_TO_ROMAN_MAP = new HashMap<Integer, String>() {
+		{
+			put(1, "I");
+			put(4, "IV");
+			put(5, "V");
+			put(9, "IX");
+			put(10, "X");
+			put(40, "XL");
+			put(50, "L");
+			put(90, "XC");
+			put(100, "C");
+			put(400, "CD");
+			put(500, "D");
+			put(900, "CM");
+			put(1000, "M");
+		}
+	};
+
+	public static Map<String, Integer> ROMAN_TO_INTEGER = new HashMap<String, Integer>() {
+		{
+			put("I", 1);
+			put("V", 5);
+			put("X", 10);
+			put("L", 50);
+			put("C", 100);
+			put("D", 500);
+			put("M", 1000);
+		}
+	};
+
+	private static Integer[] BASES = { 1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1 };
+
+	public static void main(String[] args) {
+		// System.out.println(toRoman(666));
+		System.out.println(toInteger("DCLXVI"));
+	}
+
+	public static String toRoman(int num) {
+
+		StringBuilder result = new StringBuilder();
+
+		for (int i : BASES) {
+			while (num >= i) {
+				result.append(INTEGER_TO_ROMAN_MAP.get(i));
+				num = num - i;
+			}
+		}
+
+		return result.toString();
+	}
+
+	public static Integer toInteger(String str) {
+		// Initialize result
+		Integer res = 0;
+
+		for (int i = 0; i < str.length(); i++) {
+			// Getting value of symbol s[i]
+			Integer s1 = ROMAN_TO_INTEGER.get(String.valueOf(str.charAt(i)));
+
+			// Getting value of symbol s[i+1]
+			if (i + 1 < str.length()) {
+				Integer s2 = ROMAN_TO_INTEGER.get(String.valueOf(str.charAt(i + 1)));
+
+				// Comparing both values
+				if (s1 >= s2) {
+					// Value of current symbol is greater
+					// or equalto the next symbol
+					res = res + s1;
+				} else {
+					res = res + s2 - s1;
+					i++; // Value of current symbol is
+					// less than the next symbol
+				}
+			} else {
+				res = res + s1;
+				i++;
+			}
+		}
+
+		return res;
+	}
+}