二分查找

1.基础版

public int search(int[] nums, int target) {
        int i = 0, j = nums.length - 1;
        while (i <= j) {
            int middle = (i + j) >>> 1;
            if (target < nums[middle]) {
                j = middle - 1;
            } else if (target > nums[middle]) {
                i = middle + 1;
            } else {
                return middle;
            }
        }
        return -1;
}

2.改动版

public int search(int[] nums, int target) {
        int i = 0, j = nums.length;
        while (i < j) {
            int middle = (i + j) >>> 1;
            if (target < nums[middle]) {
                j = middle;
            } else if (target > nums[middle]) {
                i = middle + 1;
            } else {
                return middle;
            }
        }
        return -1;
}

3.平衡版

public int search(int[] nums, int target) {
        int i = 0, j = nums.length;
        while (i + 1 < j) {
            int middle = (i + j) >>> 1;
            if (target < nums[middle]) {
                j = middle;
            } else {
                i = middle;
            }
        }
        return nums[i] == target ? i : -1;
}