题目描述:
给定一个 n 个元素有序的(升序)整型数组 nums 和一个目标值 target ,写一个函数搜索 nums 中的 target,如果目标值存在返回下标,否则返回 -1。
解析:
1.left = 0, right = nums.length - 1, mid = left + (right - left) / 2
2.当left <= right,如果mid上的值等于target,返回mid,如果小于target,则left = mid + 1(砍掉左半边),如果大于target,则right = mid - 1(砍掉右半边)
3.如果while循环结束后都没有找到target,则返回-1
Java:
public int search(int[] nums, int target) {
int left = 0, right = nums.length - 1;
while(left <= right) {
int mid = left + (right - left) / 2;
if(nums[mid] == target) {
return mid;
} else if(nums[mid] < target) {
left = mid + 1;
} else {
right = mid - 1;
}
}
return -1;
}
JavaScript:
var search = function(nums, target) {
let left = 0, right = nums.length - 1;
while(left <= right) {
mid = Math.floor(left + (right - left) / 2);
if(nums[mid] === target) {
return mid;
} else if(nums[mid] < target) {
left = mid + 1;
} else {
right = mid - 1;
}
}
return -1;
};