二分查找模板

java语言的二分查找模板

• left < right - 1
• mid = left + (right - left) / 2 向下取整
• 找到相等的情况下， 向左向右看看
• 最后同时要判断下标是left 与 right 的数组值

class Solution {
    public int findT(int[] nums, int target, boolean isRight) {
        if(nums == null || nums.length == 0) {
            return -1;
        }
        int left = 0;
        int right = nums.length - 1;
        int mid = -1;
        while(left < right - 1) {
            mid = left + (right - left) / 2;
            if(nums[mid] > target) {
                right = mid - 1;
            }else if(nums[mid] < target) {
                left = mid + 1;
            }else { // 重点，相等的情况下， 继续想右边看看有没有相等的
                if(isRight) {
                    left = mid;
                }else {
                    right = mid;
                }
            }
        }
        if( false == isRight) {
            if(nums[left] == target) {
                return left;
            }else if(nums[right] == target) {
                return right;
            }
        }else {
            if(nums[right] == target) {
                return right;
            }else if(nums[left] == target) {
                return left;
            }
        }
        return -1;
    }

}