經典二分法

Find any position of a target number in a sorted array. Return -1 if target does not exist.

java實現

public class Solution {
    /*
     * @param nums: An integer array sorted in ascending order
     * @param target: An integer
     * @return: An integer
     */
    public int findPosition(int[] nums, int target) {
        // write your code here
        if (nums == null || nums.length == 0) {
            return -1;
        }
        int left = 0, right = nums.length - 1;
        int mid = 0;
        while (left + 1 < right) {
            mid = (left + right) / 2;
            if (nums[mid] == target) {
                return mid;
            } else if (nums[mid] > target) {
                right = mid;
            } else {
                left = mid;
            }
        }
        if (nums[left] == target) {
            return left;
        }
        if (nums[right] == target) {
            return right;
        }
        return -1;
    }
}

python實現

注意點：在python3.x中，除法運算與2.x有所不同，使用的是double類型的除法

“//”可以完成地板除

class Solution:
    """
    @param: nums: An integer array sorted in ascending order
    @param: target: An integer
    @return: An integer
    """
    def findPosition(self, nums, target):
        # write your code here
        if nums == None or len(nums) == 0:
            return -1
        left, right = 0, len(nums) - 1
        while left + 1 < right:
            mid = (left + right) // 2
            if nums[mid] == target:
                return mid
            if nums[mid] > target:
                right = mid
            else:
                left = mid
        if nums[left] == target:
            return left
        if nums[right] == target:
            return right
        return -1