60-binary-2-pointer.cpp

#include <iostream>
#include <vector>
#include <utility> /* for using pair datatype. */
using namespace std;

vector<int> FirstLast(vector<int> nums, int target){
    int n = nums.size();
    int l1 = 0, r1 = n-1, p1, l2=0, r2=n-1,p2, a1=-1,a2=-1;

    while (l1<=r1 || l2<=r2){
        if (l1<=r1)p1 = l1 + (r1-l1)/2;
        if (l2<=r2) p2 = l2 + (r2-l2)/2;

        if (nums[p1] == target){ 
            a1 = p1;
            r1 = p1-1;
        }
        if (nums[p2] == target){
            a2 = p2;
            l2 = p2+1;
        }

        if (nums[p1]<target) l1 = p1+1;
        if (nums[p2] < target) l2 = p2 + 1;
    
        if (nums[p1]>target) r1 = p1-1;
        if (nums[p2] > target) r2 = p2 - 1;
    
    }  

    return vector<int> {a1,a2};
} 

int main() {
    vector<int> myArr = {1,2,4,5,5,5,5,6,90};
    cout<< FirstLast(myArr, 5)[0] << " " << FirstLast(myArr, 5)[1] << endl;
    return 0;
}