Leetcoe高频题(八) 我就不信邪了 LeetCode 二分法

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35. 搜索插入位置

class Solution {
    
    
  public int searchInsert(int[] nums, int target) {
    
    
    int high = nums.length - 1;
     int low = 0;
     while ( low <= high ) {
    
    
         int mid = (low + high ) >>1;
         if ( target > nums[mid]) {
    
    
             low = mid + 1;
         }else if ( target < nums[mid]) {
    
    
             high = mid - 1;
         }else {
    
    
             return mid;
         }
     }
     return low;
}
}

162. 寻找峰值

class Solution {
    
    
    public int findPeakElement(int[] nums) {
    
     

     if(nums.length==0||nums==null) return -1;

     if(nums.length==1)  return 0;
 
       int l=0;
       int r=nums.length-1;

       while(l<r){
    
    
       int mid=(r-l)/2+l;
         if(nums[mid]<nums[mid+1]) l=mid+1;
         else r=mid;
       }
       return l;  

    }
}

NC48 二分查找

import java.util.*;


public class Solution {
    
    
     
    public int upper_bound_ (int n, int v, int[] a) {
    
    
        int i=0;
        int j=n-1;
        int index=n+1;
       
       if (v > a[n - 1]) return n + 1;     //如果最大值小于查找值则直接返回
        
        
//         [2,3,4]  1
//         [2,3,4,4,5] 4 
        while(i<j){
    
    
           int mid=(i+j)/2; 
           if(a[mid]>=v){
    
    
            j=mid;   
           } 
           else{
    
    
               i=mid+1;
           }   
        } 
         return  i+1;
    } 
}

NC105 转动过得有序数组中寻找目标值

import java.util.*;


public class Solution {
    
    
    /**
     * 
     * @param A int整型一维数组 
     * @param target int整型 
     * @return int整型
     */
    public int search (int[] A, int target) {
    
    
        // write code hereint
        int len = A.length;
        int left = 0;
        int right = len-1;

        while(left <= right)
        {
    
    
           int middle = (right+left)>>1;
           if(A[middle] == target)
                return middle;
           if(A[left] <= A[middle])  /// left side is sorted
           {
    
    
               if(A[left] <= target && target < A[middle])
                   right = middle-1;//[3,5,7,8,1,2] 5
               else
                   left = middle+1;//[6,7,1,2,3,4,5] 3
           }
           else                     /// right side is sorted
           {
    
    
               if(A[middle] < target && target <= A[right])
                    left = middle+1;  //[6,7,1,2,3,4,5] 3
               else
                    right = middle-1;//[3,5,7,8,1,2] 5
           }
        }
        return -1;
    }
   
}