LIOJ 1041：String trim
- 解題想法：一開始是想碰到字以後就結束，但是字不一定是英文字母，也有可能是標點符號或其他之類的，那這樣就不成立了。另外一個重點是，這樣寫沒辦法去掉後面的空白。
function solve(lines) {
let s = lines[0]
console.log(trim(s))
//BTW, 寫成這樣就好了 console.log(trim(lines[0]))
}
// LIOJ 1041：String trim
function trim(str) {
let result = ''
for(let i=0; i<str.length; i++) {
// if(str[i] >= a && str[i] <= z) {
// break
// }
if(str[i] !== ' ') {
result += str[i]
}
}
return str
}
看了解答發現要分成幾個部份，第一個是去掉前面的空白 + 遇到字以後就留下來；第二個是去掉後面的空白，這時候要用迴圈倒著跑，可是輸入會有問題，因此最後的 result += str[i] 要寫成 result = str[i] + result
flag variable，reference: What is a flag variable?
A flag variable, in its simplest form, is a variable you define to have one value until some condition is true, in which case you change the variable's value. It is a variable you can use to control the flow of a function or statement, allowing you to check for certain conditions while your function progresses.
- 我把 flag variable 當作是一個條件式，先設為 true or false，當某個條件成立時，在這個案例裡面是「當遇到字串時」
var readline = require('readline');
var lines = []
var rl = readline.createInterface({
input: process.stdin
});
rl.on('line', function (line) {
lines.push(line)
});
rl.on('close', function() {
solve(lines)
})
function solve(lines) {
console.log(trim(lines[0]))
}
// LIOJ 1041：String trim
function trim(str) {
let result = ''
//下面這行是一個 flag variable
let FrontSpaceEnds = false
for(let i=0; i<str.length; i++) {
if(str[i] !== ' ' || FrontSpaceEnds) {
FrontSpaceEnds = true
result += str[i]
}
}
let result2 = ''
let BackSpaceEnds = false
for(let i=result.length - 1; i>=0; i--) {
if(result[i] !== ' ' || BackSpaceEnds) {
BackSpaceEnds = true
result2 = result[i] + result2
}
}
return result2
}
LIOJ 1042：String toLowerCase
- Make an imitation of String toLowerCase function
var readline = require('readline');
var lines = []
var rl = readline.createInterface({
input: process.stdin
});
rl.on('line', function (line) {
lines.push(line)
});
rl.on('close', function() {
solve(lines)
})
function solve(lines) {
console.log(toLowerCase(lines[0]))
}
function toLowerCase(str) {
let result = ''
for(let i=0; i<str.length; i++) {
if(str[i] >= 'A' && str[i] <= 'Z') {
//OJ出現 runtime error，所以要寫一個
//let code = str.charCodeAt(i)
//下面有正解
result += String.fromCharCode(str.charCodeAt(i) + 32)
} else {
result += str[i]
}
}
return result
}
var readline = require('readline');
var lines = []
var rl = readline.createInterface({
input: process.stdin
});
rl.on('line', function (line) {
lines.push(line)
});
rl.on('close', function() {
solve(lines)
})
function solve(lines) {
console.log(toLowerCase(lines[0]))
}
function toLowerCase(str) {
let result = ''
for(let i=0; i<str.length; i++) {
if(str[i] >= 'A' && str[i] <= 'Z') {
let code = str.charCodeAt(i)
result += String.fromCharCode(code + 32)
} else {
result += str[i]
}
}
return result
}
LIOJ 1043：String endsWith
- Make an imitation of String endsWith function
- 解題想法：從後面開始找，迴圈倒著跑，每一項去比對，比到 target 的長度就結束
- 這是福爾摩斯的演繹法，先刪去所有不可能，剩下的就是可能，我好久沒看福爾摩斯了...也好久沒吃摩斯漢堡了，懷念～
When you have eliminated the impossible, whatever remains, however improbable, must be the truth.
---Arthur Conan Doyle
var readline = require('readline');
var lines = []
var rl = readline.createInterface({
input: process.stdin
});
rl.on('line', function (line) {
lines.push(line)
});
rl.on('close', function() {
solve(lines)
})
function solve(lines) {
let str = lines[0]
let target = lines[1]
console.log(endsWith(str, target))
}
function endsWith(str, searchString) {
if(searchString.length > str.length) {
return false
}
let strIndex = str.length - 1
let searchStrIndex = searchString.length - 1
while(searchStrIndex >= 0) {
if(str[strIndex] !== searchString[searchStrIndex]) {
return false
}
strIndex--
searchStrIndex--
}
return true
}
LIOJ 1044：String padEnd
- Make an imitation of String padEnd function
- 解題想法：先處理原本字串的長度已經大於等於規定的長度時，就直接回傳原字串；接著就是把新字串加上舊字串，然後把多餘的長度截掉
var readline = require('readline');
var lines = []
var rl = readline.createInterface({
input: process.stdin
});
rl.on('line', function (line) {
lines.push(line)
});
rl.on('close', function() {
solve(lines)
})
function solve(lines) {
let str = lines[0]
let targetLength = Number(lines[1])
let padString = lines[2]
console.log(padEnd(str, targetLength, padString))
}
function padEnd(str, targetLength, padString) {
if(str.length >= targetLength) {
return str
}
let result = str
while(result.length < targetLength){
result += padString
}
let newResult = ''
for(let i=0; i<targetLength; i++) {
newResult += result[i]
}
return newResult
}
LIOJ 1045：String slice
Make an imitation of String slice function
解題想法：跑個迴圈吧
var readline = require('readline');
var lines = []
var rl = readline.createInterface({
input: process.stdin
});
rl.on('line', function (line) {
lines.push(line)
});
rl.on('close', function() {
solve(lines)
})
function solve(lines) {
console.log(slice(lines[0], Number(lines[1]), Number(lines[2])))
}
function slice(str, beginIndex, endIndex) {
let result = ''
for(let i=beginIndex; i<=endIndex - 1; i++) {
result += str[i]
}
return result
}
