add pset6 solutions

pset6/README.md

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+https://docs.cs50.net/2018/x/psets/6/pset6.html

pset6/sentimental/README.md

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+https://docs.cs50.net/2018/x/psets/6/sentimental/sentimental

pset6/sentimental/caesar/README.md

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+https://docs.cs50.net/2018/x/psets/2/caesar/caesar.html

pset6/sentimental/caesar/caesar.py

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+import sys
+from cs50 import get_string
+
+
+def main():
+    if len(sys.argv) != 2:
+        print("Usage: ./caesar k")
+        sys.exit(1)
+
+    k = int(sys.argv[1])
+    plaintext = get_string("plaintext: ")
+
+    print("ciphertext: ", end="")
+
+    for ch in plaintext:
+        if not ch.isalpha():
+            print(ch, end="")
+            continue
+
+        ascii_offset = 65 if ch.isupper() else 97
+
+        pi = ord(ch) - ascii_offset
+        ci = (pi + k) % 26
+
+        print(chr(ci + ascii_offset), end="")
+
+    print()
+
+    return 0
+
+
+if __name__ == "__main__":
+    main()

pset6/sentimental/cash/README.md

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+https://docs.cs50.net/2018/x/psets/1/cash/cash.html

pset6/sentimental/cash/cash.py

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+from cs50 import get_float
+from math import floor
+
+
+def main():
+    while True:
+        dollars_owed = get_float("Change owed: ")
+        cents_owed = floor(dollars_owed * 100)
+
+        if cents_owed > 0:
+            break
+
+    quarters = cents_owed // 25
+    dimes = (cents_owed % 25) // 10
+    nickels = ((cents_owed % 25) % 10) // 5
+    pennies = ((cents_owed % 25) % 10) % 5
+
+    print(f"{quarters + dimes + nickels + pennies}")
+
+
+if __name__ == "__main__":
+    main()

pset6/sentimental/crack/README.md

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+https://docs.cs50.net/2018/x/psets/2/crack/crack.html

pset6/sentimental/crack/crack.py

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+import sys
+import crypt
+
+
+def main():
+    if len(sys.argv) != 2:
+        print("Usage: crack <hash>")
+        sys.exit(1)
+
+    ahash = sys.argv[1]
+    salt = ahash[0:2]
+    letters = " abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+
+    for fifth in letters:
+        for fourth in letters:
+            for third in letters:
+                for second in letters:
+                    for first in letters[1:]:
+                        candidate = f"{first}{second}{third}{fourth}{fifth}".strip()
+
+                        if crypt.crypt(candidate, salt) == ahash:
+                            print(candidate)
+                            sys.exit(0)
+
+
+if __name__ == "__main__":
+    main()

pset6/sentimental/credit/README.md

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+https://docs.cs50.net/2018/x/psets/1/credit/credit.html

pset6/sentimental/credit/credit.py

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+from cs50 import get_int
+from math import floor
+
+
+def main():
+    digit1 = 0
+    digit2 = 0
+    num_digits = 0
+    sum_of_double_odds = 0
+    sum_of_evens = 0
+    cc_number = get_int("Number: ")
+
+    while cc_number > 0:
+        digit2 = digit1
+        digit1 = cc_number % 10
+
+        if num_digits % 2 == 0:
+            sum_of_evens += digit1
+        else:
+            multiple = 2 * digit1
+            sum_of_double_odds += (multiple // 10) + (multiple % 10)
+
+        cc_number //= 10
+        num_digits += 1
+
+    is_valid = (sum_of_evens + sum_of_double_odds) % 10 == 0
+    first_two_digits = (digit1 * 10) + digit2
+
+    if digit1 == 4 and num_digits >= 13 and num_digits <= 16 and is_valid:
+        print("VISA\n")
+    elif first_two_digits >= 51 and first_two_digits <= 55 and num_digits == 16 and is_valid:
+        print("MASTERCARD\n")
+    elif (first_two_digits == 34 or first_two_digits == 37) and num_digits == 15 and is_valid:
+        print("AMEX\n")
+    else:
+        print("INVALID\n")
+
+
+if __name__ == "__main__":
+    main()

pset6/sentimental/hello/README.md

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+https://docs.cs50.net/2018/x/psets/1/hello/hello.html

pset6/sentimental/hello/hello.py

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+def main():
+    print("hello, world")
+
+if __name__ == "__main__":
+    main()

pset6/sentimental/mario/less/README.md

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+https://docs.cs50.net/2018/x/psets/1/mario/less/mario.html

pset6/sentimental/mario/less/mario.py

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+from cs50 import get_int
+
+
+def main():
+    while True:
+        height = get_int("Height: ")
+        width = height + 1
+        if height >= 0 and height <= 23:
+            break
+
+    for i in range(1, height + 1):
+        num_hashes = i + 1
+        num_spaces = width - num_hashes
+
+        print(" " * num_spaces, end="")
+        print("#" * num_hashes)
+
+
+if __name__ == "__main__":
+    main()

pset6/sentimental/mario/more/README.md

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+https://docs.cs50.net/2018/x/psets/1/mario/more/mario.html

pset6/sentimental/mario/more/mario.py

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+from cs50 import get_int
+
+
+def main():
+    while True:
+        height = get_int("Height: ")
+        width = height
+        if height >= 0 and height <= 23:
+            break
+
+    for i in range(1, height + 1):
+        num_hashes = i
+        num_spaces = width - num_hashes
+
+        print(" " * num_spaces, end="")
+        print("#" * num_hashes, end="")
+
+        print("  ", end="")
+
+        print("#" * num_hashes)
+
+
+if __name__ == "__main__":
+    main()

pset6/sentimental/vigenere/README.md

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+https://docs.cs50.net/2018/x/psets/2/vigenere/vigenere.html

pset6/sentimental/vigenere/vigenere.py

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+import sys
+from cs50 import get_string
+
+
+def is_valid(k):
+    for ch in k:
+        if not ch.isalpha():
+            return False
+    return True
+
+
+def main():
+    if len(sys.argv) != 2 or not is_valid(sys.argv[1]):
+        print("Usage: ./vigenere k")
+        sys.exit(1)
+
+    k = sys.argv[1]
+    plaintext = get_string("plaintext: ")
+    j = 0
+
+    print("ciphertext: ", end="")
+
+    for ch in plaintext:
+        if not ch.isalpha():
+            print(ch, end="")
+            continue
+
+        ascii_offset = 65 if ch.isupper() else 97
+
+        pi = ord(ch) - ascii_offset
+        kj = ord(k[j % len(k)].upper()) - 65
+        ci = (pi + kj) % 26
+        j += 1
+
+        print(chr(ci + ascii_offset), end="")
+
+    print()
+
+    return 0
+
+
+if __name__ == "__main__":
+    main()

pset6/similarities/less/README.md

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+https://docs.cs50.net/2018/x/psets/6/similarities/less/similarities.html

pset6/similarities/less/application.py

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+import cs50
+import re
+from flask import Flask, abort, redirect, render_template, request
+from html import escape
+from werkzeug.exceptions import default_exceptions, HTTPException
+
+from helpers import lines, sentences, substrings
+
+# Web app
+app = Flask(__name__)
+
+
+@app.after_request
+def after_request(response):
+    """Disable caching"""
+    response.headers["Cache-Control"] = "no-cache, no-store, must-revalidate"
+    response.headers["Expires"] = 0
+    response.headers["Pragma"] = "no-cache"
+    return response
+
+
+@app.route("/")
+def index():
+    """Handle requests for / via GET (and POST)"""
+    return render_template("index.html")
+
+
+@app.route("/compare", methods=["POST"])
+def compare():
+    """Handle requests for /compare via POST"""
+
+    # Read files
+    if not request.files["file1"] or not request.files["file2"]:
+        abort(400, "missing file")
+    try:
+        file1 = request.files["file1"].read().decode("utf-8")
+        file2 = request.files["file2"].read().decode("utf-8")
+    except Exception:
+        abort(400, "invalid file")
+
+    # Compare files
+    if not request.form.get("algorithm"):
+        abort(400, "missing algorithm")
+    elif request.form.get("algorithm") == "lines":
+        regexes = [f"^{re.escape(match)}$" for match in lines(file1, file2)]
+    elif request.form.get("algorithm") == "sentences":
+        regexes = [re.escape(match) for match in sentences(file1, file2)]
+    elif request.form.get("algorithm") == "substrings":
+        if not request.form.get("length"):
+            abort(400, "missing length")
+        elif not int(request.form.get("length")) > 0:
+            abort(400, "invalid length")
+        regexes = [re.escape(match) for match in substrings(
+            file1, file2, int(request.form.get("length")))]
+    else:
+        abort(400, "invalid algorithm")
+
+    # Highlight files
+    highlights1 = highlight(file1, regexes)
+    highlights2 = highlight(file2, regexes)
+
+    # Output comparison
+    return render_template("compare.html", file1=highlights1, file2=highlights2)
+
+
+def highlight(s, regexes):
+    """Highlight all instances of regexes in s."""
+
+    # Get intervals for which strings match
+    intervals = []
+    for regex in regexes:
+        if not regex:
+            continue
+        matches = re.finditer(regex, s, re.MULTILINE)
+        for match in matches:
+            intervals.append((match.start(), match.end()))
+    intervals.sort(key=lambda x: x[0])
+
+    # Combine intervals to get highlighted areas
+    highlights = []
+    for interval in intervals:
+        if not highlights:
+            highlights.append(interval)
+            continue
+        last = highlights[-1]
+
+        # If intervals overlap, then merge them
+        if interval[0] <= last[1]:
+            new_interval = (last[0], interval[1])
+            highlights[-1] = new_interval
+
+        # Else, start a new highlight
+        else:
+            highlights.append(interval)
+
+    # Maintain list of regions: each is a start index, end index, highlight
+    regions = []
+
+    # If no highlights at all, then keep nothing highlighted
+    if not highlights:
+        regions = [(0, len(s), False)]
+
+    # If first region is not highlighted, designate it as such
+    elif highlights[0][0] != 0:
+        regions = [(0, highlights[0][0], False)]
+
+    # Loop through all highlights and add regions
+    for start, end in highlights:
+        if start != 0:
+            prev_end = regions[-1][1]
+            if start != prev_end:
+                regions.append((prev_end, start, False))
+        regions.append((start, end, True))
+
+    # Add final unhighlighted region if necessary
+    if regions[-1][1] != len(s):
+        regions.append((regions[-1][1], len(s), False))
+
+    # Combine regions into final result
+    result = ""
+    for start, end, highlighted in regions:
+        escaped = escape(s[start:end])
+        if highlighted:
+            result += f"<span>{escaped}</span>"
+        else:
+            result += escaped
+    return result
+
+
+@app.errorhandler(HTTPException)
+def errorhandler(error):
+    """Handle errors"""
+    return render_template("error.html", error=error), error.code
+
+
+# https://github.com/pallets/flask/pull/2314
+for code in default_exceptions:
+    app.errorhandler(code)(errorhandler)