Valid parentheses

Signed-off-by: begeekmyfriend <[email protected]>

020_valid_parentheses/Makefile

@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test valid_parentheses.c

020_valid_parentheses/valid_parentheses.c

@@ -0,0 +1,47 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+static bool isValid(char *s)
+{
+    int n = 0, cap = 100;
+    char *stack = malloc(cap);
+
+    while (*s != '\0') {
+        switch(*s) {
+        case '(':
+        case '[':
+        case '{':
+            if (n + 1 >= cap) {
+                cap *= 2;
+                stack = realloc(stack, cap);
+            }
+            stack[n++] = *s;
+            break;
+        case ')':
+            if (stack[--n] != '(') return false;
+            break;
+        case ']':
+            if (stack[--n] != '[') return false;
+            break;
+        case '}':
+            if (stack[--n] != '{') return false;
+            break;
+        default:
+            return false;
+        }
+        s++;
+    }
+
+    return n == 0;
+}
+
+int main(int argc, char **argv)
+{
+    if (argc != 2) {
+        fprintf(stderr, "Usage: ./test xxxx");
+        exit(-1);
+    }
+    printf("%s\n", isValid(argv[1]) ? "true" : "false");
+    return 0;
+}