Solution for: array partition I

Author: edyluisrey

src/leetcode/ArrayPartitionI.java

@@ -0,0 +1,54 @@
+package leetcode;
+
+public class ArrayPartitionI {
+
+	public static void main(String[] args) {
+		// TODO Auto-generated method stub
+
+	}
+		public int arrayPairSum(int[] nums) {
+		    mergeSort(nums,0, nums.length-1); 
+		    int sum=0;
+		    for(int i=0; i< nums.length; i+=2){
+		        sum= sum+ nums[i];
+		    }
+		    return sum;
+		}
+		
+		public void mergeSort(int[] nums, int l, int p){
+		    if(l==p){
+		        return;
+		    }
+		    int mid = (l+p)/2;
+		    mergeSort(nums, l, mid);
+		    mergeSort(nums, mid+1, p);
+		    merge(nums, l, mid+1, p);
+		}
+		
+		public void merge(int[] nums, int left, int mid, int rightEnd){
+		    int right = mid;  
+		    int k=0;
+		    int n= rightEnd-left+1;
+		    int lower =left;
+		    int[] temp= new int[n]; 
+		    while(left<=mid-1 &&  right<= rightEnd){
+		    	if(nums[left]<=nums[right]){
+		    		temp[k++]= nums[left++];
+		    	}else{
+		    		temp[k++]= nums[right++];
+		    	}
+		    } 
+		    while(left<=mid-1){
+		    	temp[k++]= nums[left++];
+		    }
+		    while(right<=rightEnd){
+		    	temp[k++]= nums[right++];
+		    }
+		    
+		    for(int i=0; i<n;i++){
+		    	nums[lower+i] = temp[i];
+		    }
+			
+		}
+
+}