Each day I solve several coding challenges and puzzles from Codr's ranked mode. The goal is to reach genius rank, along the way I explain how I solve them. You do not need any programming background to get started, and you will learn a ton of new and interesting things as you go.
function RPN(tokens) { const stack = []; for (let index = 0; index < tokens.length; index++) { const token = tokens[index]; if (!Number.isNaN(Number(token))) { stack.push(token); } else { const a = Number(stack.pop()); const b = Number(stack.pop()); if (token === '*') { stack.push(b * a); } else if (token === '/') { stack.push(b / a); } else if (token === '+') { stack.push(b + a); } else if (token === '-') { stack.push(b - a); } } } return stack.pop(); } let arr = ['1', '8', '5', '6', '+', '5', '*', '/', '*', '6', '+', '7', '+'] let A = RPN(arr); A = Math.floor(A) // A = ? (number) Our good old friend the Reverse Polish Notation (RPN) is back again. To complete the challenge we have to solve the notation, let's do that in pseudo-code:
arr = 1 8 5 6 + 5 * / * 6 + 7 + stack = [] index: 0, 1, 2 & 3 stack = [1 8 5 6] index: 4 token: + push(5 + 6 = 11) stack = [1 8 11] index: 5 stack = [1 8 11 5] index: 5 token: * push(11 * 5 = 55) stack = [1 8 55] index: 6 token: / push(8 / 55 = 0.145) stack = [1 0.145] index: 7 token: * push(0.145 * 1 = 0.145) stack = [0.145] index: 8 stack = [0.145 6] index: 9 token: + push(0.145 + 6 = 6.145) stack = [6.145] index: 10 stack = [6.145 7] index: 11 token: + push(6.145 + 7 = 13.145) stack = [13.145] A = Floor(stack.pop()) A == 13 
By solving these challenges you train yourself to be a better programmer. You'll learn newer and better ways of analyzing, debugging and improving code. As a result you'll be more productive and valuable in business. Get started and become a certified Codr today at https://nevolin.be/codr/
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