c_cpp SearchInRange，二分查找

Posted 2021-05-14

#include<bits/stdc++.h>
using namespace std;

int rangeL(vector<int> nums, int target){
    int l=0,r=nums.size()-1;
    while(l<=r){
        int mid=l+(r-l)/2;
        if(mid==0){
            if(nums[mid]==target){
                return mid;
            }
        }
        if(nums[mid]==target && nums[mid-1]!=target){
            return mid;
        }
        if(nums[mid]<target){
            l=mid+1;
        }else{
            r=mid-1;
        }
    }
    return -1;
}
int rangeR(vector<int> nums, int target){
    int l=0,r=nums.size()-1;
    while(l<=r){
        int mid=l+(r-l)/2;
        if(mid==nums.size()-1){
            if(nums[mid]==target){
                return mid;
            }
        }
        if(nums[mid]==target && nums[mid+1]!=target){
            return mid;
        }
        if(nums[mid]>target){
            r=mid-1;
        }else{
            l=mid+1;
        }
    }
    return -1;
}
vector<int> searchRange(vector<int>& nums, int target) {
    int start=0,end=nums.size()-1;
    vector<int> ans={-1,-1};
    ans[0]=rangeL(nums,target);
    ans[1]=rangeR(nums,target);
    return ans;
}
int main(){
    int t;
    cin>>t;
    while(t--){
        int n;
        cin>>n;
        vector<int> a(n);
        for(int i=0;i<n;i++){
            cin>>a[i];
        }
        int x;
        cin>>x;
        vector<int> ans=searchRange(a,x);
        cout<<ans[0]<<" "<<ans[1]<<endl;
    }
    return 0;
}