Soring&Searching 合并两个有序数组 @CareerCup

merge，要点是从后往前走

package Sorting_Searching;

import CtCILibrary.AssortedMethods;

/**
 * You are given two sorted arrays, A and B, and A has a large enough buffer at
 * the end to hold B. Write a method to merge B into A in sorted order.
 * 
 * 译文：
 * 
 * A和B是两个有序数组(假设为递增序列)，而且A的长度足以放下A和B中所有的元素， 写一个函数将数组B融入数组A，并使其有序。
 * 
 */
public class S11_1 {

	public static void main(String[] args) {
		int[] a = { 2, 3, 4, 5, 6, 8, 10, 100, 0, 0, 0, 0, 0, 0 };
		int[] b = { 1, 4, 5, 6, 7, 7 };
		merge(a, b, 8, 6);
		System.out.println(AssortedMethods.arrayToString(a));
	}

	/** Merges array
     * @param a first array
     * @param b second array
     * @param lastA number of "real" elements in a
     * @param lastB number of "real" elements in b
     */
    public static void merge(int[] a, int[] b, int lastA, int lastB) {
    	int mergedPos = a.length-1;
    	int aPos = lastA-1;
    	int bPos = lastB-1;
    	while(aPos>=0 && bPos>=0){
    		if(a[aPos] >= b[bPos]){
    			a[mergedPos] = a[aPos];
    			aPos--;
    		}else{
    			a[mergedPos] = b[bPos];
    			bPos--;
    		}
    		mergedPos--;
    	}
    	
    	// 可省略，因为本来元素就在a中
    	while(aPos >= 0){
    		a[mergedPos--] = a[aPos--];
    	}
    	
    	while(bPos >= 0){
    		a[mergedPos--] = b[bPos--];
    	}
    }
    
    
}