🤖 takeUforward pattern problems | pattern | javascript

Apr 13, 2023

🗒️ Problems

Recently I saw the following article <br /> Really? Anyway, I tried to solve these.

Must do Pattern Problems before starting DSA

🍀 General guideline

There are 4 general rules for solving a pattern-based question :

We always use nested loops for printing the patterns.
- For the outer loop, we count the number of lines/rows and loop for them.
- Next, for the inner loop, we focus on the number of columns and somehow connect them to the rows by forming a logic such that for each row we get the required number of columns to be printed.
We print the numbers inside the inner loop.
Observe symmetry in the pattern or check if a pattern is a combination of two or more similar patterns or not.

Pattern-1: Rectangular Star Pattern

const N = 5;

for (let r = 0; r < N; r += 1) {
  console.log("*".repeat(N));
}

*****
*****
*****
*****
*****

Pattern-2: Right-Angled Triangle Pattern

const N = 6;

for (let r = 0; r < N; r += 1) {
  console.log("*".repeat(r + 1));
}

*
**
***
****
*****
******

Pattern – 3: Right-Angled Number Pyramid

const N = 5;

const genString = (num) => {
  let str = "";
  for (let i = 1; i <= num; i += 1) {
    str += "" + i;
  }
  return str;
};

for (let i = 1; i <= N; i += 1) {
  console.log(genString(i));
}

Pattern – 4: Right-Angled Number Pyramid – II

const N = 5;

const genString = (num) => {
  return String(num).repeat(num);
};

for (let i = 1; i <= N; i += 1) {
  console.log(genString(i));
}

Pattern-5: Inverted Right Pyramid

const N = 5;

for (let i = N; i >= 1; i -= 1) {
  console.log("*".repeat(i));
}

*****
****
***
**
*

Pattern – 6: Inverted Numbered Right Pyramid

const N = 5;

const genString = (num) => {
  let str = "";
  for (let i = 1; i <= num; i += 1) {
    str += "" + i;
  }
  return str;
};

for (let i = N; i >= 1; i -= 1) {
  console.log(genString(i));
}

Pattern – 7: Star Pyramid

||||| * ||||||
    * * *
   ** * **
  *** * ***
 **** * ****
***** * *****

const N = 5;

const genString = (row) => {
  let str = "";
  str += " ".repeat(N - row);
  str += "*".repeat(row);
  str += "*";
  str += "*".repeat(row);
  str += " ".repeat(N - row);
  return str;
};

for (let r = 0; r < N; r += 1) {
  console.log(genString(r));
}

     *
    ***
   *****
  *******
 *********

Pattern – 8: Inverted Star Pyramid

const N = 6;

const genString = (row) => {
  let str = "";
  str += " ".repeat(N - row);
  str += "*".repeat(row - 1);
  str += "*";
  str += "*".repeat(row - 1);
  str += " ".repeat(N - row);
  return str;
};

for (let r = N; r >= 1; r -= 1) {
  console.log(genString(r));
}

***********
 *********
  *******
   *****
    ***
     *

Pattern – 9: Diamond Star Pattern

N = 3

||*
|***
*****

*****
 ***
  *

const N = 6;

const genUpperString = (row) => {
  let str = "";
  str += " ".repeat(N - row);
  str += "*".repeat(row - 1);
  str += "*";
  str += "*".repeat(row - 1);
  str += " ".repeat(N - row);
  return str;
};

const genLowerString = (row) => {
  let str = "";
  str += " ".repeat(row - 1);
  str += "*".repeat(N - row);
  str += "*";
  str += "*".repeat(N - row);
  str += " ".repeat(row - 1);
  return str;
};

for (let r = 1; r <= N; r += 1) {
  console.log(genUpperString(r));
}
for (let r = 1; r <= N; r += 1) {
  console.log(genLowerString(r));
}

     *
    ***
   *****
  *******
 *********
***********
***********
 *********
  *******
   *****
    ***
     *

Pattern – 10: Half Diamond Star Pattern

      1 23456
1     * |||||
2     * *
3     * **
4     * ***
5     * ****

6     * *****

5     * ****
4     * ***
3     * **
2     * *
1     *

const N = 6;

const genString = (row) => {
  let str = "*";
  str += "*".repeat(row - 1);
  str += " ".repeat(N - row);
  return str;
};

for (let r = 1; r < N; r += 1) {
  console.log(genString(r));
}

console.log(genString(N));

for (let r = N - 1; r >= 1; r -= 1) {
  console.log(genString(r));
}

*
**
***
****
*****
******
*****
****
***
**
*

Pattern – 11: Binary Number Triangle Pattern

const N = 5;

const genString = (num, startFromOdd) => {
  let str = "";
  let cur = startFromOdd ? 1 : 0;
  for (let i = 1; i <= num; i += 1) {
    str += "" + cur;
    cur = (cur + 1) % 2;
  }
  return str;
};

for (let i = 1; i <= N; i += 1) {
  console.log(genString(i, i % 2));
}

Pattern – 12: Number Crown Pattern

   123456
1  1           1
2  12         21
3  12        321
4  1234     4321
5  12345   54321
6  123456 654321

const N = 6;

const genString = (row) => {
  let str = "";
  for (let c = 1; c <= row; c += 1) {
    str += "" + c;
  }
  str += " ".repeat(N - row);
  str += " ".repeat(N - row);
  for (let c = row; c >= 1; c -= 1) {
    str += "" + c;
  }
  return str;
};

for (let r = 1; r <= N; r += 1) {
  console.log(genString(r));
}

1          1
12        21
123      321
1234    4321
12345  54321
123456654321

Pattern – 13: Increasing Number Triangle Pattern

    1   2   3   4   5  6
1   1
2   2   3
3   4   5   6
4   7   8   9  10
5  11  12  13  14  15
6  16  17  18  19  20  21

const N = 6;

let cur = 1;

const genString = (row) => {
  const local = [];
  for (let c = 1; c <= row; c += 1) {
    local.push(cur);
    cur += 1;
  }
  return local.join(" ");
};

for (let r = 1; r <= N; r += 1) {
  console.log(genString(r));
}

1
2 3
4 5 6
7 8 9 10
11 12 13 14 15
16 17 18 19 20 21

Pattern-14: Increasing Letter Triangle Pattern

   1 2 3 4 5 6
1  A
2  A B
3  A B C
4  A B C D
5  A B C D E
6  A B C D E F

const N = 6;

const genString = (row) => {
  const local = [];
  for (let c = 0; c < row; c += 1) {
    local.push(String.fromCharCode(c + "A".charCodeAt(0)));
  }
  return local.jon(" ");
};

for (let r = 1; r <= N; r += 1) {
  console.log(genString(r));
}

A
A B
A B C
A B C D
A B C D E
A B C D E F

Pattern-15: Reverse Letter Triangle Pattern

   1 2 3 4 5 6
1  A B C D E F
2  A B C D E
3  A B C D
4  A B C
5  A B
6  A

const N = 6;

const genString = (row) => {
  const local = [];
  for (let c = 0; c < row; c += 1) {
    local.push(String.fromCharCode(c + "A".charCodeAt(0)));
  }
  return local.join(" ");
};

for (let r = N; r >= 1; r -= 1) {
  console.log(genString(r));
}

A B C D E F
A B C D E
A B C D
A B C
A B
A

Pattern – 16: Alpha-Ramp Pattern

   1 2 3 4 5 6
1  A
2  B B
3  C C C
4  D D D D
5  E E E E E
6  F F F F F F

const N = 6;

const genString = (row) => {
  const local = [];
  for (let c = 0; c < row; c += 1) {
    local.push(String.fromCharCode(row - 1 + "A".charCodeAt(0)));
  }
  return local.join(" ");
};

for (let r = 1; r <= N; r += 1) {
  console.log(genString(r));
}

A
B B
C C C
D D D D
E E E E E
F F F F F F

Pattern – 17: Alpha-Hill Pattern


1        A
2      A B A
3     AB C BA
4    ABC D CBA
5   ABCD E DCBA
6  ABCDE F EDCBA
   12345 6 78901

const N = 6;

const genString = (row) => {
  let str = "";
  const spaces = " ".repeat(N - row);
  let local = "";
  for (let c = 1; c < row; c += 1) {
    local += String.fromCharCode(c - 1 + "A".charCodeAt(0));
  }

  str += spaces;
  str += local;
  str += String.fromCharCode(row - 1 + "A".charCodeAt(0));
  str += local.split("").reverse().join("");
  str += spaces;
  return str;
};

for (let r = 1; r <= N; r += 1) {
  console.log(genString(r));
}

Pattern-18: Alpha-Triangle Pattern

1  F
2  E F
3  D E F
4  C D E F
5  B C D E F
6  A B C D E F
   1 2 3 4 5 6

const N = 6;

const genString = (row) => {
  const local = [];
  for (let c = 0; c <= row; c += 1) {
    local.push(String.fromCharCode(N - c - 1 + "A".charCodeAt(0)));
  }
  return local.reverse().join(" ");
};

for (let r = 0; r < N; r += 1) {
  console.log(genString(r));
}

F
E F
D E F
C D E F
B C D E F
A B C D E F

Pattern-19: Symmetric-Void Pattern

   123456
1  *** ***
2  **| |**
3  *|| ||*

4  *    *
5  **  **
6  ******

const N = 3;

const genString = (row) => {
  let str = "";
  str += "*".repeat(N + 1 - row);
  str += " ".repeat(row - 1);
  str += " ".repeat(row - 1);
  str += "*".repeat(N + 1 - row);
  return str;
};

for (let r = 1; r <= N; r += 1) {
  console.log(genString(r));
}
for (let r = N; r >= 1; r -= 1) {
  console.log(genString(r));
}

******
**  **
*    *
*    *
**  **
******

Pattern – 20: Symmetric-Butterfly Pattern

N = 6
   123456 789012
1  *||||| |||||*
2  **|||| ||||**
3  ***||| |||***
4  ****|| ||****
5  *****| |*****

6  ************

7  *****  *****
8  ****    ****
9  ***      ***
0  **        **
1  *          *

const N = 6;

const genString = (row) => {
  let str = "";
  let local = "";
  local += "*".repeat(row);
  local += " ".repeat(N - row);

  str += local;
  str += local.split("").reverse().join("");
  return str;
};

for (let r = 1; r < N; r += 1) {
  console.log(genString(r));
}

console.log("*".repeat(N * 2));

for (let r = N - 1; r >= 1; r -= 1) {
  console.log(genString(r));
}

*          *
**        **
***      ***
****    ****
*****  *****
************
*****  *****
****    ****
***      ***
**        **
*          *

Pattern – 21: Hollow Rectangle Pattern

const N = 4;

const genString = (num) => {
  if (num === 1 || num === N) return "*".repeat(N);
  return "*" + " ".repeat(N - 2) + "*";
};

for (let i = 1; i <= N; i += 1) {
  console.log(genString(i));
}

****
*  *
*  *
****

ProbPattern – 22: The Number Patternlem

   1 2 3 4 5  6  7 8 9 0 1
0  6 6 6 6 6  6  6 6 6 6 6
1  6 5 5 5 5  5  5 5 5 5 6
2  6 5 4 4 4  4  4 4 4 5 6
3  6 5 4 3 3  3  3 3 4 5 6
4  6 5 4 3 2  2  2 3 4 5 6

5  6 5 4 3 2  1  2 3 4 5 6

6  6 5 4 3 2 2 2 3 4 5 6
7  6 5 4 3 3 3 3 3 4 5 6
8  6 5 4 4 4 4 4 4 4 5 6
9  6 5 5 5 5 5 5 5 5 5 6
0  6 6 6 6 6 6 6 6 6 6 6

const N = 6;

const genString = (row) => {
  const local = [];
  const temp = [];
  for (let c = 0; c < N - 1; c += 1) {
    temp.push(Math.max(N - row, N - c));
  }
  local.push(...temp);
  local.push(N - row);
  local.push(...temp.reverse());
  return local.join(" ");
};

for (let r = 0; r < N; r += 1) {
  console.log(genString(r));
}

for (let r = N - 2; r >= 0; r -= 1) {
  console.log(genString(r));
}

6 6 6 6 6 6 6 6 6 6 6
6 5 5 5 5 5 5 5 5 5 6
6 5 4 4 4 4 4 4 4 5 6
6 5 4 3 3 3 3 3 4 5 6
6 5 4 3 2 2 2 3 4 5 6
6 5 4 3 2 1 2 3 4 5 6
6 5 4 3 2 2 2 3 4 5 6
6 5 4 3 3 3 3 3 4 5 6
6 5 4 4 4 4 4 4 4 5 6
6 5 5 5 5 5 5 5 5 5 6
6 6 6 6 6 6 6 6 6 6 6

📚 Reference

Must do Pattern Problems before starting DSA