fd

Author: dingjikerbo

leetcode/solution/src/ValidParentheses.java

@@ -3,40 +3,34 @@
  */
 public class ValidParentheses {
 
-    // 耗时5ms
+    // 耗时4ms
     public boolean isValid(String s) {
-        char[] stack = new char[s.length()];
-        int top = -1;
-
-        for (char c : s.toCharArray()) {
-            switch (c) {
+        int[] stack = new int[s.length()];
+        int index = 0;
+        for (int i = 0; i < s.length(); i++) {
+            switch (s.charAt(i)) {
+                case '(':
+                case '[':
+                case '{':
+                    stack[index++] = i;
+                    break;
                 case ')':
-                    if (top >= 0 && stack[top] == '(') {
-                        top--;
-                    } else {
+                    if (index == 0 || s.charAt(stack[--index]) != '(') {
                         return false;
                     }
                     break;
-                case '}':
-                    if (top >= 0 && stack[top] == '{') {
-                        top--;
-                    } else {
+                case ']':
+                    if (index == 0 || s.charAt(stack[--index]) != '[') {
                         return false;
                     }
                     break;
-                case ']':
-                    if (top >= 0 && stack[top] == '[') {
-                        top--;
-                    } else {
+                case '}':
+                    if (index == 0 || s.charAt(stack[--index]) != '{') {
                         return false;
                     }
                     break;
-                default:
-                    stack[++top] = c;
-                    break;
             }
         }
-
-        return top < 0;
+        return index == 0;
     }
 }

leetcode/src/Main.java

@@ -2,42 +2,36 @@
 
 public class Main {
 
-    public double findMedianSortedArrays(int[] nums1, int[] nums2) {
-        int len1 = nums1.length;
-        int len2 = nums2.length;
-        int total = len1 + len2;
-        if (total % 2 == 0) {
-            return (findKth(nums1, nums2, 0, len1 - 1, 0, len2 - 1, total/2) +
-                    findKth(nums1, nums2, 0, len1 - 1, 0, len2 - 1, total/2 + 1))/2.0f;
-        } else {
-            return findKth(nums1, nums2, 0, len1 - 1, 0, len2 - 1, total/2 + 1);
+    public boolean isValid(String s) {
+        int[] stack = new int[s.length()];
+        int index = 0;
+        for (int i = 0; i < s.length(); i++) {
+            switch (s.charAt(i)) {
+                case '(':
+                case '[':
+                case '{':
+                    stack[index++] = i;
+                    break;
+                case ')':
+                    if (index == 0 || s.charAt(stack[--index]) != '(') {
+                        return false;
+                    }
+                    break;
+                case ']':
+                    if (index == 0 || s.charAt(stack[--index]) != '[') {
+                        return false;
+                    }
+                    break;
+                case '}':
+                    if (index == 0 || s.charAt(stack[--index]) != '{') {
+                        return false;
+                    }
+                    break;
+            }
         }
+        return index == 0;
     }
 
-    public double findKth(int[] nums1, int[] nums2, int start1, int end1, int start2, int end2, int k) {
-        int len1 = end1 - start1 + 1;
-        int len2 = end2 - start2 + 1;
-        if (len1 > len2) {
-            return findKth(nums2, nums1, start2, end2, start1, end1, k);
-        }
-        if (len1 == 0) {
-            return nums2[start2 + k - 1];
-        }
-        if (k == 1) {
-            return Math.min(nums1[start1], nums2[start2]);
-        }
-        int ia = Math.min(k/2, len1);
-        int ib = k - ia;
-        if (nums1[start1 + ia - 1] > nums2[start2 + ib - 1]) {
-            return findKth(nums1, nums2, start1, end1, start2 + ib, end2, k - ib);
-        } else if (nums1[start1 + ia - 1] < nums2[start2 + ib - 1]) {
-            return findKth(nums1, nums2, start1 + ia, end1, start2, end2, k - ia);
-        } else {
-            return nums1[start1 + ia - 1];
-        }
-    }
-
-
     public static void main(String[] args) {
 
     }