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Two Pointer

  • 2 pointers are used - left & right, slow & fast depending on the situation

Find if there is a pair with sum x in sorted array​

def pair_sum_x(arr, x):
    N = len(arr)
    l, r = 0, N - 1
    while l < r:
        if arr[l] + arr[r] == x:
            return True
        elif arr[l] + arr[r] < x:
            l += 1
        else:
            r -= 1
    return False