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704. Binary Search

Description

Given an array of integers nums which is sorted in ascending order, and an integer target, write a function to search target in nums. If target exists, then return its index. Otherwise, return -1.

You must write an algorithm with O(log n) runtime complexity.

 

Example 1:

Input: nums = [-1,0,3,5,9,12], target = 9
Output: 4
Explanation: 9 exists in nums and its index is 4

Example 2:

Input: nums = [-1,0,3,5,9,12], target = 2
Output: -1
Explanation: 2 does not exist in nums so return -1

 

Constraints:

  • 1 <= nums.length <= 104
  • -104 < nums[i], target < 104
  • All the integers in nums are unique.
  • nums is sorted in ascending order.

Solutions

  • class Solution {
        public int search(int[] nums, int target) {
            int left = 0, right = nums.length - 1;
            while (left < right) {
                int mid = (left + right) >> 1;
                if (nums[mid] >= target) {
                    right = mid;
                } else {
                    left = mid + 1;
                }
            }
            return nums[left] == target ? left : -1;
        }
    }
    
  • class Solution {
    public:
        int search(vector<int>& nums, int target) {
            int left = 0, right = nums.size() - 1;
            while (left < right) {
                int mid = left + right >> 1;
                if (nums[mid] >= target)
                    right = mid;
                else
                    left = mid + 1;
            }
            return nums[left] == target ? left : -1;
        }
    };
    
  • class Solution:
        def search(self, nums: List[int], target: int) -> int:
            left, right = 0, len(nums) - 1
            while left < right:
                mid = (left + right) >> 1
                if nums[mid] >= target:
                    right = mid
                else:
                    left = mid + 1
            return left if nums[left] == target else -1
    
    
  • func search(nums []int, target int) int {
    	left, right := 0, len(nums)-1
    	for left < right {
    		mid := (left + right) >> 1
    		if nums[mid] >= target {
    			right = mid
    		} else {
    			left = mid + 1
    		}
    	}
    	if nums[left] == target {
    		return left
    	}
    	return -1
    }
    
  • /**
     * @param {number[]} nums
     * @param {number} target
     * @return {number}
     */
    var search = function (nums, target) {
        let left = 0;
        let right = nums.length - 1;
        while (left < right) {
            const mid = (left + right) >> 1;
            if (nums[mid] >= target) {
                right = mid;
            } else {
                left = mid + 1;
            }
        }
        return nums[left] == target ? left : -1;
    };
    
    
  • use std::cmp::Ordering;
    
    impl Solution {
        pub fn search(nums: Vec<i32>, target: i32) -> i32 {
            let mut l = 0;
            let mut r = nums.len();
            while l < r {
                let mid = (l + r) >> 1;
                match nums[mid].cmp(&target) {
                    Ordering::Less => {
                        l = mid + 1;
                    }
                    Ordering::Greater => {
                        r = mid;
                    }
                    Ordering::Equal => {
                        return mid as i32;
                    }
                }
            }
            -1
        }
    }
    
    
  • public class Solution {
        public int Search(int[] nums, int target) {
            int left = 0, right = nums.Length - 1;
            while (left < right) {
                int mid = (left + right) >> 1;
                if (nums[mid] >= target) {
                    right = mid;
                } else {
                    left = mid + 1;
                }
            }
            return nums[left] == target ? left : -1;
        }
    }
    
  • function search(nums: number[], target: number): number {
        let [l, r] = [0, nums.length - 1];
        while (l < r) {
            const mid = (l + r) >> 1;
            if (nums[mid] >= target) {
                r = mid;
            } else {
                l = mid + 1;
            }
        }
        return nums[l] === target ? l : -1;
    }
    
    

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