improved num 4

Author: chihungyu1116

4. Median of Two Sorted Arrays.js

@@ -1,46 +1,94 @@
+// /**
+//  * @param {number[]} nums1
+//  * @param {number[]} nums2
+//  * @return {number}
+//  */
+ 
+// // http://blog.csdn.net/yutianzuijin/article/details/11499917
+// var findMedianSortedArrays = function(nums1, nums2) {
+//     var m = nums1.length;
+//     var n = nums2.length;
+//     var total = m + n;
+    
+//     if(total%2 === 1) {
+//         return findKth(nums1, m, nums2, n, parseInt(total/2) + 1);
+//     } else {
+//         return (findKth(nums1, m, nums2, n, parseInt(total/2)) + findKth(nums1, m, nums2, n, parseInt(total/2) + 1))/2;
+//     }
+// };
+
+
+// function findKth(a, m, b, n, k) {
+//     // always assume that m is equal or smaller than n
+//     if(m > n) {
+//         return findKth(b, n, a, m, k);
+//     }
+    
+//     if(m === 0) {
+//         return b[k-1];
+//     }
+    
+//     if(k === 1) {
+//         return Math.min(a[0],b[0]);
+//     }
+    
+//     // divide k into two parts
+//     var pa = Math.min(parseInt(k/2), m);
+//     var pb = k - pa;
+    
+//     if(a[pa - 1] < b[pb - 1]) {
+//         return findKth(a.slice(pa), m - pa, b, n, k - pa);
+//     } else if(a[pa - 1] > b[pb - 1]) {
+//         return findKth(a, m, b.slice(pb), n - pb, k - pb);
+//     } else {
+//         return a[pa - 1];
+//     }
+// }
+
+
 /**
  * @param {number[]} nums1
  * @param {number[]} nums2
  * @return {number}
  */
- 
-// http://blog.csdn.net/yutianzuijin/article/details/11499917
 var findMedianSortedArrays = function(nums1, nums2) {
-    var m = nums1.length;
-    var n = nums2.length;
-    var total = m + n;
+    var total = nums1.length + nums2.length;
 
-    if(total%2 === 1) {
-        return findKth(nums1, m, nums2, n, parseInt(total/2) + 1);
+    if (total % 2 === 1) {
+        return findKth(nums1, 0, nums2, 0, parseInt(total/2) + 1);
     } else {
-        return (findKth(nums1, m, nums2, n, parseInt(total/2)) + findKth(nums1, m, nums2, n, parseInt(total/2) + 1))/2;
+        return (
+            findKth(nums1, 0, nums2, 0, parseInt(total/2))
+            + findKth(nums1, 0, nums2, 0, parseInt(total/2) + 1)
+        )/2;
     }
 };
 
-
-function findKth(a, m, b, n, k) {
-    // always assume that m is equal or smaller than n
-    if(m > n) {
-        return findKth(b, n, a, m, k);
+function findKth(nums1, start1, nums2, start2, kth) {
+    var len1 = nums1.length - start1;
+    var len2 = nums2.length - start2;
+    
+    if (len1 > len2) {
+        return findKth(nums2, start2, nums1, start1, kth);
     }
 
-    if(m === 0) {
-        return b[k-1];
+    if (len1 === 0) {
+        return nums2[kth - 1];
     }
 
-    if(k === 1) {
-        return Math.min(a[0],b[0]);
+    if (kth === 1) {
+        return Math.min(nums1[start1], nums2[start2]);
     }
 
-    // divide k into two parts
-    var pa = Math.min(parseInt(k/2), m);
-    var pb = k - pa;
+    // divide kth into 2 parts
+    var part1 = Math.min(parseInt(kth/2), len1);
+    var part2 = kth - part1;
 
-    if(a[pa - 1] < b[pb - 1]) {
-        return findKth(a.slice(pa), m - pa, b, n, k - pa);
-    } else if(a[pa - 1] > b[pb - 1]) {
-        return findKth(a, m, b.slice(pb), n - pb, k - pb);
+    if (nums1[start1 + part1 - 1] < nums2[start2 + part2 - 1]) {
+        return findKth(nums1, start1 + part1, nums2, start2, kth - part1);
+    } else if (nums1[start1 + part1 - 1] > nums2[start2 + part2 - 1]) {
+        return findKth(nums1, start1, nums2, start2 + part2, kth - part2);
     } else {
-        return a[pa - 1];
+        return nums1[start1 + part1 - 1];
     }
 }