剑指Offer 53I - 在排序数组中查找数字 I

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number}
 */
var search = function(nums, target) {
    if(!nums.length)    return 0;
    if(nums.length === 1)   return target===nums[0] ? 1 : 0;
    
    let leftBound = -1, rightBound = nums.length;
    
    //找左边界
    let start = 0, end = nums.length-1;
    while(start + 1 < end){
        const mid = parseInt((start + end) / 2);
        if(nums[mid] < target){
            start = mid;
        }else{
            end = mid;
        }
    }
    if(nums[start] !== target){
        leftBound = start;
    }

    //找右边界
    start = leftBound;
    end = nums.length-1;
    while(start + 1 < end){
        const mid = parseInt((start + end) / 2);
        if(nums[mid] > target){
            end = mid;
        }else{
            start = mid;
        }
    }
    if(nums[end] !== target){
        rightBound = end;
    }
    
    
    return rightBound - leftBound - 1;
};