Create Solution.java

Author: Jerring

solution/0227.Basic Calculator II/Solution.java

@@ -0,0 +1,52 @@
+class Solution {
+    public int calculate(String s) {
+        char[] cs = s.toCharArray();
+        Deque<Character> op = new ArrayDeque<>();
+        Deque<Integer> num = new ArrayDeque<>();
+        for (int i = 0; i < cs.length; ++i) {
+            if (cs[i] == '*' || cs[i] == '/') {
+                op.push(cs[i]);
+            } else if (cs[i] == '+' || cs[i] == '-') {
+                if (!op.isEmpty()) {
+                    calc(op, num);
+                }
+                op.push(cs[i]);
+            } else if (Character.isDigit(cs[i])) {
+                int j = i;
+                int k = 0;
+                while (j < cs.length && Character.isDigit(cs[j])) {
+                    k = k * 10 + cs[j] - '0';
+                    ++j;
+                }
+                i = j - 1;
+                num.push(k);
+                if (!op.isEmpty() && (op.peek() == '*' || op.peek() == '/')) {
+                    calc(op, num);
+                }
+            }
+        }
+        while (!op.isEmpty()) {
+            calc(op, num);
+        }
+        return num.peek();
+    }
+
+    private void calc(Deque<Character> op, Deque<Integer> num) {
+        int y = num.pop();
+        int x = num.pop();
+        switch (op.pop()) {
+            case '*':
+                num.push(x * y);
+                break;
+            case '/':
+                num.push(x / y);
+                break;
+            case '+':
+                num.push(x + y);
+                break;
+            default:
+                num.push(x - y);
+                break;
+        }
+    }
+}