add problem 32 and test function

Author: supercoderhawk

C/1-50/32-Longest-Valid-Parentheses.c

@@ -0,0 +1,50 @@
+/*
+ * Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring.
+
+ * For "(()", the longest valid parentheses substring is "()", which has length = 2.
+
+ * Another example is ")()())", where the longest valid parentheses substring is "()()", which has length = 4.
+ * Created by supercoderx on 2017/8/12.
+ */
+#include <stdio.h>
+int longestValidParentheses(char* s) {
+    int len = 0;
+    char* ch = s;
+    while(*ch!='\0'){
+        ch++;
+        len++;
+    }
+    if(len == 0)
+        return 0;
+    int stack[len],top = -1, longest = -1;
+    for(int i = 0;i < len;i++){
+      if(s[i]=='(')
+          stack[++top] = i;
+      else{
+          if(top>-1){
+            if(s[stack[top]] == '(')
+                top--;
+            else
+                stack[++top] = i;
+          }else
+              stack[++top] = i;
+      }
+    }
+    if(top == -1)
+        return len;
+
+    int a=len,b,curLen = -1;
+    while(top>-1){
+        b = stack[top];
+        curLen = a-b-1;
+        longest = longest>curLen?longest:curLen;
+        a = b;
+        top--;
+    }
+    return a>longest?a:longest;
+}
+
+void testLongestValidParentheses(){
+    char* s1 = "()(())";
+    printf("%d",longestValidParentheses(s1));
+}