string add Bracket matching problem

dai · dai · commit 2e387308fd2c · 2021-03-31T11:58:22.000+08:00
diff --git a/27-算法面试专题-字符串.md b/27-算法面试专题-字符串.md
@@ -134,5 +134,41 @@ public class StringUtil {
         }
         return true;
     }
+
+
+    /**
+     * 5、括号字符匹配问题：输入一个字符串，包含'(','[','{',')',']','}'几种括号，求是否是括号匹配的结果。
+     * @param s
+     * @return
+     */
+    public static boolean isValid(String s) {
+
+        if (s == null || s.length() == 0) {
+            return true;
+        }
+
+        char[] str = s.toCharArray();
+        Stack<Character> stack = new Stack<>();
+
+        for (int i = 0; i < str.length; i++) {
+            char cha = str[i];
+            // 遇到左括号，添加相应的右括号
+            if (cha == '(' || cha == '[' || cha == '{') {
+                stack.add(cha == '(' ? ')' : (cha == '[' ? ']' : '}'));
+            } else { // 遇到右括号，弹出栈，比对相等
+                if (stack.isEmpty()) {
+                    return false;
+                }
+                char last = stack.pop();
+                if (cha != last) {
+                    return false;
+                }
+            }
+        }
+
+        // 遍历结束，栈刚好为空。满足匹配要求
+        return stack.isEmpty();
+    }
+
 }
 ```
