167. Two Sum II - Input array is sorted

167. Two Sum II - Input array is sort

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Given an array of integers that is already sorted in ascending order, find two numbers such that they add up to a specific target number.

The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are not zero-based.

You may assume that each input would have exactly one solution and you may not use the same element twice.

Input: numbers={2, 7, 11, 15}, target=9
Output: index1=1, index2=2

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题意：

在一个排好序的数组里面寻找两个数之和等于target的

注意的是数组里面只有唯一的一直值等于target

返回值是两个数的index值

算法思路：

设置两个变量，一个从开头，一个从结尾开始向中间走

如果二者之和大于target，结尾的数减一

如果二者之和小于target，开头的数加一

如果相等，返回下标加一

代码：

package easy;
/*
@author wchstrife
@version 2017年8月21日下午9:12:07
*/
public class TwoSumIIInputarrayissorted {

	public int[] twoSum(int[] numbers, int target) {
		
        int i = 0, j = numbers.length-1;
        int tmp = 0;
        
        while(i < j){
        	tmp = numbers[i] + numbers[j];
        	if(tmp > target){
        		j--;
        	}else if (tmp < target) {
				i++;
			}else {
				
				return new int[]{i+1, j+1};
			}
        }
        
        return null;
    }
}