Find Upper and Lower Bound

#1

Please look into my code and tell me whats the error.

#2

#include #include using namespace std; int upperBound(int *a, int n, int key){ int left = 0; int right = n - 1; int ans = -1; while(left <= right){ int mid = (left + right)/2; if(a[mid] == key){ ans = key; left = mid + 1; }else if(a[mid] > key){ right = mid - 1; }else{ left = mid + 1; } } return ans; } int lowerBound(int *a, int n, int key){ int left =0; int right = n - 1; int ans = -1; while(left<= right){ int mid = (left + right)/2; if(a[mid] == key){ ans = mid; right = mid - 1; }else if(a[mid] < key){ left = mid + 1; }else{ right = mid - 1; } } return ans; } int main() { int n; cin>>n; int arr[100000]; for(int i=0; i<n; i++){ cin>>arr[i]; } int times; cin>>times; while(times–){ int t; cin>>t; cout<<lowerBound(arr, n, t)<<" "<<upperBound(arr, n, t)<<endl; } return 0; }

#3

for input
4
1 1 1 1
2
1
2

Your Code’s Output
0 -1
-1 -1

Correct Output
0 3
-1 -1

your Condition is not correct

Simple And Correct condition will be like this

int val;
		cin>>val;
		int lb=lower_bound(a,a+n,val)-a;
		if(val > a[n-1] || a[lb]>val){
			//element not found
			cout<<"-1 -1"<<endl;
		}else{
			// element found in the array
			// now find upper bound 
			int ub = upper_bound(a,a+n,val)-a -1 ;
			cout<<lb<<" "<<ub<<endl;
		}
#4

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