Today I have done Guess Number Higher or Lower and leetcode's March LeetCoding Challenge with cpp.

Guess Number Higher or Lower

Description

We are playing the Guess Game. The game is as follows:

I pick a number from 1 to n. You have to guess which number I picked.

Every time you guess wrong, I will tell you whether the number I picked is higher or lower than your guess.

You call a pre-defined API int guess(int num), which returns 3 possible results:

• -1: The number I picked is lower than your guess (i.e. pick < num).
• 1: The number I picked is higher than your guess (i.e. pick > num).
• 0: The number I picked is equal to your guess (i.e. pick == num).

Return the number that I picked.

Example 1:

Input: n = 10, pick = 6
Output: 6

Example 2:

Input: n = 1, pick = 1
Output: 1

Example 3:

Input: n = 2, pick = 1
Output: 1

Example 4:

Input: n = 2, pick = 2
Output: 2

Constraints:

• 1 <= n <= 231 - 1
• 1 <= pick <= n

Solution

/** 
 * Forward declaration of guess API.
 * @param  num   your guess
 * @return 	     -1 if num is lower than the guess number
 *			      1 if num is higher than the guess number
 *               otherwise return 0
 * int guess(int num);
 */

class Solution {
public:
    int guessNumber(int n) {
        int begin = 1, end = n;
        while(begin < end) {
            int mid = begin + (end - begin) / 2;
            int res = guess(mid);
            if(res != 1) {
                end = mid;
            } else {
                begin = mid + 1;
            }
        }
        return begin;
    }
};

March LeetCoding Challenge 10

Description

Integer to Roman

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.

Symbol       Value
I             1
V             5
X             10
L             50
C             100
D             500
M             1000

For example, 2 is written as II in Roman numeral, just two one's added together. 12 is written as XII, which is simply X + II. The number 27 is written as XXVII, which is XX + V + II.

Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not IIII. Instead, the number four is written as IV. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as IX. There are six instances where subtraction is used:

• I can be placed before V (5) and X (10) to make 4 and 9.
• X can be placed before L (50) and C (100) to make 40 and 90.
• C can be placed before D (500) and M (1000) to make 400 and 900.

Given an integer, convert it to a roman numeral.

Example 1:

Input: num = 3
Output: "III"

Example 2:

Input: num = 4
Output: "IV"

Example 3:

Input: num = 9
Output: "IX"

Example 4:

Input: num = 58
Output: "LVIII"
Explanation: L = 50, V = 5, III = 3.

Example 5:

Input: num = 1994
Output: "MCMXCIV"
Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.

Constraints:

• 1 <= num <= 3999

Solution

class Solution {
    vector<pair<int, int>> p = {
        {1000, 100},
        {500, 100},
        {100, 10},
        {50, 10},
        {10, 1},
        {5, 1},
        {1, 0}
    };
    unordered_map<int, char> mp = {
        {1000, 'M'},
        {500, 'D'},
        {100, 'C'},
        {50, 'L'},
        {10, 'X'},
        {5, 'V'},
        {1, 'I'}
    };
public:
    string intToRoman(int num) {
        string answer;
        for(auto [larger, less] : p) {
            while(num >= larger) {
                num -= larger;
                answer.push_back(mp[larger]);
            }
            if(num >= larger - less) {
                num -= larger - less;
                answer.push_back(mp[less]);
                answer.push_back(mp[larger]);
            }
        }
        return move(answer);
    }
};