算法各种模板以及公式

1,二分：

public static int binarySearch(int[] nums, int target) {
        if(nums == null || nums.length == 0) {
            return -1;
        }
        int start = 0;
        int end = nums.length - 1;
        while (start <= end){
            int mid = start + (end - start) / 2;
            if (nums[mid] == target){
                return mid;
            } else if (nums[mid] < target) {
                start = mid + 1;
            } else {
                end = mid - 1;
            }
        }
        return -1;
    }