Sitrone
diff --git a/‎solutions/394. Decode String/DecodeString.java‎
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diff --git a/‎solutions/415. Add Strings/AddStrings.java‎
Lines changed: 38 additions & 0 deletions b/‎solutions/415. Add Strings/AddStrings.java‎
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+package leetcode;
+
+import java.util.Stack;
+
+public class DecodeString {
+
+	public static void main(String[] args) {
+		// TODO Auto-generated method stub
+		/*
+		 * StringBuilder sb = new StringBuilder("abcd"); sb.reverse();
+		 * System.out.println(sb.toString()); int num = 1; while(num-- > 0){
+		 * sb.append(sb); } System.out.println(sb.toString());
+		 */
+
+		String s = "2[abc]3[cd]ef";
+		String t = "100[leetcode]";
+		System.out.println(decodeString(s));
+		
+		System.out.println(evl("(1+((2+3)*(4*5)))"));
+
+	}
+
+	/**
+	 * 双栈，一个栈装数字，一个栈装字符串
+	 * @param s
+	 * @return
+	 */
+	public static String decodeString(String s) {
+		Stack<StringBuilder> strStack = new Stack<>();
+		Stack<Integer> intStack = new Stack<>();
+
+		StringBuilder cur = new StringBuilder("");
+		int num = 0;
+		for (int i = 0; i < s.length(); i++) {
+			char c = s.charAt(i);
+			if (c == '[') {
+				intStack.push(num);
+				strStack.push(cur);
+				cur = new StringBuilder("");
+				num = 0;
+			} else if (c == ']') {
+				StringBuilder temp = cur;
+				cur = strStack.pop();
+				for (num = intStack.pop(); num > 0; --num){
+					cur.append(temp);
+				}
+			} else if (Character.isDigit(c)) {
+				num = num * 10 + c - '0';
+			} else {
+				cur.append(c);
+			}
+		}
+
+		return cur.toString();
+	}
+	
+	/**
+	 * 同类体型，具体参见<算法4>
+	 * Dijkstra的双栈算术表达式
+	 * @param str
+	 * @return
+	 */
+	public static Double evl(String str){
+        Stack<Double> vals = new Stack<Double>();
+        Stack<Character> op = new Stack<Character>();
+        char[] ch = str.toCharArray();
+        for(int i = 0;i < ch.length;i++){
+            if(ch[i] == '+') op.push(ch[i]);
+            else if(ch[i] == '-') op.push(ch[i]);
+            else if(ch[i] == '*') op.push(ch[i]);
+            else if(ch[i] == '/') op.push(ch[i]);
+            else if(ch[i] == '(');
+            else if(ch[i] == ')'){
+                char o = op.pop();
+                Double val = vals.pop();
+                if(o == '+') val = val + vals.pop();
+                else if(o == '-') val = vals.pop() - val;
+                else if(o == '*') val = vals.pop() * val;
+                else if(o == '/') val = vals.pop() / val;
+                vals.push(val);
+            }else{
+                vals.push(Double.parseDouble(Character.toString(ch[i])));
+            }
+        }
+        return vals.pop();
+    }
+
+}
@@ -0,0 +1,38 @@
+package leetcode;
+
+public class AddStrings {
+
+	public static void main(String[] args) {
+		// TODO Auto-generated method stub
+		System.out.println(addStrings("99999", "11"));
+	}
+
+	/**
+	 * ´óÊýÏà¼Ó
+	 * @param num1
+	 * @param num2
+	 * @return
+	 */
+	public static String addStrings(String num1, String num2) {
+		int sum = 0, carry = 0;
+		StringBuilder sb = new StringBuilder();
+
+		int i = num1.length() - 1, j = num2.length() - 1;
+		while (i >= 0 || j >= 0) {
+			if (i >= 0 && j >= 0) {
+				sum = (int) (num1.charAt(i) - '0') + (int) (num2.charAt(j) - '0') + carry;
+			} else if (i >= 0) {
+				sum = (int) (num1.charAt(i) - '0') + carry;
+			} else if (j >= 0) {
+				sum = (int) (num2.charAt(j) - '0') + carry;
+			}
+			carry = sum / 10;
+			sb.append(sum % 10);
+			i--;
+			j--;
+		}
+		if (carry == 1)
+			sb.append("1");
+		return sb.reverse().toString();
+	}
+}