Modified 2 solutions

varunu28 · varunu28 · commit d886046a5962 · 2020-02-05T06:56:05.000-08:00
diff --git a/Easy/Array Partition I.java b/Easy/Array Partition I.java
@@ -1,11 +1,20 @@
 class Solution {
-    public int arrayPairSum(int[] nums) {
-        Arrays.sort(nums);
-        int sum = 0;
-        for (int i = 0; i < nums.length; i += 2) {
-            sum += nums[i];
+  public int arrayPairSum(int[] nums) {
+    int[] arr = new int[20001];
+    for (int num : nums) {
+      arr[num + 10000]++;
+    }
+    int sum = 0;
+    boolean odd = true;
+    for (int i = 0; i < arr.length; i++) {
+      while (arr[i] > 0) {
+        if (odd) {
+          sum += i - 10000;
         }
-        
-        return sum;
+        odd = !odd;
+        arr[i]--;
+      }
     }
+    return sum;
+  }
 }
diff --git a/Easy/Count and Say.java b/Easy/Count and Say.java
@@ -1,32 +1,23 @@
 class Solution {
-    public String countAndSay(int n) {
-        String first = "1";
-        String str = "11";
-        
-        if (n == 1) return first;
-        if (n == 2) return str;
-        
-        for (int i = 3; i<=n; i++) {
-            str += "$";
-            int len = str.length();
-
-            int cnt = 1; 
-            String  tmp = ""; 
-            
-            for (int j = 1; j < len; j++) {
-                if (str.charAt(j) != str.charAt(j-1)) {
-                    tmp += String.valueOf(cnt);
-                    tmp += str.charAt(j-1);
-
-                    cnt = 1;
-                }
-
-                else cnt++;
-            }
-
-            str = tmp;
-        }
-        
-        return str;
+  public String countAndSay(int n) {
+    return rec(n, "1");
+  }
+  
+  private String rec(int n, String s) {
+    if (n == 1) {
+      return s;
     }
+    StringBuilder sb = new StringBuilder();
+    int idx = 0;
+    while (idx < s.length()) {
+      char c = s.charAt(idx);
+      int count = 0;
+      while (idx < s.length() && s.charAt(idx) == c) {
+        idx++;
+        count++;
+      }
+      sb.append(count).append(c);
+    }
+    return rec(n - 1, sb.toString());
+  }
 }
