Check for characters in a string being unique
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I implemented my algorithm for checking if the string passed in is unique. I feel like my algorithm is correct, but obviously in certain cases it gives the wrong results. Why?
function isUnique(str) {
let sortedArr = str.split('').sort();
for (let [i, char] of sortedArr.entries()) {
if (char === sortedArr[i + 1]) {
return false
} else {
return true
}
}
}
console.log(isUnique('heloworld')) // truejavascript
edited Apr 3 at 11:13
Peter Mortensen
13.9k1987113
asked Apr 3 at 5:35
user3763875user3763875
745
add a comment |
I implemented my algorithm for checking if the string passed in is unique. I feel like my algorithm is correct, but obviously in certain cases it gives the wrong results. Why?
function isUnique(str) {
let sortedArr = str.split('').sort();
for (let [i, char] of sortedArr.entries()) {
if (char === sortedArr[i + 1]) {
return false
} else {
return true
}
}
}
console.log(isUnique('heloworld')) // truejavascript
edited Apr 3 at 11:13
Peter Mortensen
13.9k1987113
asked Apr 3 at 5:35
user3763875user3763875
745
FWIW:function noDuplicatedChars() { const chars = new Set(); for (let c of str) { if (chars.has(c)) return false; chars.add(c);} return true; }is a faster alternative.
– Frax
Apr 3 at 5:55
add a comment |
I implemented my algorithm for checking if the string passed in is unique. I feel like my algorithm is correct, but obviously in certain cases it gives the wrong results. Why?
function isUnique(str) {
let sortedArr = str.split('').sort();
for (let [i, char] of sortedArr.entries()) {
if (char === sortedArr[i + 1]) {
return false
} else {
return true
}
}
}
console.log(isUnique('heloworld')) // truejavascript
edited Apr 3 at 11:13
Peter Mortensen
13.9k1987113
asked Apr 3 at 5:35
user3763875user3763875
745
I implemented my algorithm for checking if the string passed in is unique. I feel like my algorithm is correct, but obviously in certain cases it gives the wrong results. Why?
function isUnique(str) {
let sortedArr = str.split('').sort();
for (let [i, char] of sortedArr.entries()) {
if (char === sortedArr[i + 1]) {
return false
} else {
return true
}
}
}
console.log(isUnique('heloworld')) // truefunction isUnique(str) {
let sortedArr = str.split('').sort();
for (let [i, char] of sortedArr.entries()) {
if (char === sortedArr[i + 1]) {
return false
} else {
return true
}
}
}
console.log(isUnique('heloworld')) // truefunction isUnique(str) {
let sortedArr = str.split('').sort();
for (let [i, char] of sortedArr.entries()) {
if (char === sortedArr[i + 1]) {
return false
} else {
return true
}
}
}
console.log(isUnique('heloworld')) // truejavascript
javascript
edited Apr 3 at 11:13
Peter Mortensen
13.9k1987113
asked Apr 3 at 5:35
user3763875user3763875
745
edited Apr 3 at 11:13
Peter Mortensen
13.9k1987113
asked Apr 3 at 5:35
user3763875user3763875
745
edited Apr 3 at 11:13
Peter Mortensen
13.9k1987113
edited Apr 3 at 11:13
Peter Mortensen
13.9k1987113
edited Apr 3 at 11:13
Peter Mortensen
13.9k1987113
13.9k1987113
asked Apr 3 at 5:35
user3763875user3763875
745
asked Apr 3 at 5:35
user3763875user3763875
745
asked Apr 3 at 5:35
user3763875user3763875
745
745
FWIW:function noDuplicatedChars() { const chars = new Set(); for (let c of str) { if (chars.has(c)) return false; chars.add(c);} return true; }is a faster alternative.
– Frax
Apr 3 at 5:55
add a comment |
FWIW:function noDuplicatedChars() { const chars = new Set(); for (let c of str) { if (chars.has(c)) return false; chars.add(c);} return true; }is a faster alternative.
– Frax
Apr 3 at 5:55
FWIW:
function noDuplicatedChars() { const chars = new Set(); for (let c of str) { if (chars.has(c)) return false; chars.add(c);} return true; } is a faster alternative.– Frax
Apr 3 at 5:55
FWIW:
function noDuplicatedChars() { const chars = new Set(); for (let c of str) { if (chars.has(c)) return false; chars.add(c);} return true; } is a faster alternative.– Frax
Apr 3 at 5:55
add a comment |
2 Answers
2
active
oldest
votes
return immediately terminates the function, so only the first iteration if your for loop will ever run. Instead, you should check for whether all characters are unique (if not, return false inside the loop), else return true after the end of the loop:
function isUnique(str) {
let sortedArr = str.split('').sort();
for(let [i,char] of sortedArr.entries()) {
if(char === sortedArr[i + 1]) {
return false
}
}
return true
}
console.log(isUnique('heloworld'))But it would probably be a lot easier to use a Set, and see if its size is equal to the length of the string:
function isUnique(str) {
return new Set(str).size === str.length;
}
console.log(isUnique('heloworld'))
console.log(isUnique('abc'))See comment, thanks Patrick: if you need to account for characters composed of multiple UCS-2 code points (𝟙𝟚𝟛😎😜🙃 etc), call the string iterator and check how many items it returns, which can be done with spread or Array.from (because otherwise, str.length won't evaluate to the right number of individual characters):
function isUnique(str) {
return new Set(str).size === [...str].length;
}
console.log(isUnique('😜'));
console.log(isUnique('😜😜'));edited Apr 3 at 6:03
Patrick Roberts
21.3k33677
answered Apr 3 at 5:37
CertainPerformanceCertainPerformance
98.4k166089
1
Not sure if this matters but for multi-unit code points you get the wrong answer, e.g.isUnique('😀😁') === false
– Patrick Roberts
Apr 3 at 5:42
5
The fix is relatively simple though:return new Set(str).size === Array.from(str).length;
– Patrick Roberts
Apr 3 at 5:50
add a comment |
Only first iteration in your for loop is run (because you always execute 'return'). Instead you can use following code
function isUnique(str, t={})
{
return ![...str].some(c=> t[c]=c in t)
}
console.log('heloworld =>',isUnique('heloworld'));
console.log('helo =>',isUnique('helo'));answered Apr 3 at 5:52
Kamil KiełczewskiKamil Kiełczewski
14.1k87397
Why isra parameter?
– JollyJoker
Apr 3 at 8:01
r (I rename it to t) is temporary hash map (define in tricky way as default param)
– Kamil Kiełczewski
Apr 3 at 8:07
add a comment |
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2 Answers
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active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
return immediately terminates the function, so only the first iteration if your for loop will ever run. Instead, you should check for whether all characters are unique (if not, return false inside the loop), else return true after the end of the loop:
function isUnique(str) {
let sortedArr = str.split('').sort();
for(let [i,char] of sortedArr.entries()) {
if(char === sortedArr[i + 1]) {
return false
}
}
return true
}
console.log(isUnique('heloworld'))But it would probably be a lot easier to use a Set, and see if its size is equal to the length of the string:
function isUnique(str) {
return new Set(str).size === str.length;
}
console.log(isUnique('heloworld'))
console.log(isUnique('abc'))See comment, thanks Patrick: if you need to account for characters composed of multiple UCS-2 code points (𝟙𝟚𝟛😎😜🙃 etc), call the string iterator and check how many items it returns, which can be done with spread or Array.from (because otherwise, str.length won't evaluate to the right number of individual characters):
function isUnique(str) {
return new Set(str).size === [...str].length;
}
console.log(isUnique('😜'));
console.log(isUnique('😜😜'));edited Apr 3 at 6:03
Patrick Roberts
21.3k33677
answered Apr 3 at 5:37
CertainPerformanceCertainPerformance
98.4k166089
1
Not sure if this matters but for multi-unit code points you get the wrong answer, e.g.isUnique('😀😁') === false
– Patrick Roberts
Apr 3 at 5:42
5
The fix is relatively simple though:return new Set(str).size === Array.from(str).length;
– Patrick Roberts
Apr 3 at 5:50
add a comment |
return immediately terminates the function, so only the first iteration if your for loop will ever run. Instead, you should check for whether all characters are unique (if not, return false inside the loop), else return true after the end of the loop:
function isUnique(str) {
let sortedArr = str.split('').sort();
for(let [i,char] of sortedArr.entries()) {
if(char === sortedArr[i + 1]) {
return false
}
}
return true
}
console.log(isUnique('heloworld'))But it would probably be a lot easier to use a Set, and see if its size is equal to the length of the string:
function isUnique(str) {
return new Set(str).size === str.length;
}
console.log(isUnique('heloworld'))
console.log(isUnique('abc'))See comment, thanks Patrick: if you need to account for characters composed of multiple UCS-2 code points (𝟙𝟚𝟛😎😜🙃 etc), call the string iterator and check how many items it returns, which can be done with spread or Array.from (because otherwise, str.length won't evaluate to the right number of individual characters):
function isUnique(str) {
return new Set(str).size === [...str].length;
}
console.log(isUnique('😜'));
console.log(isUnique('😜😜'));edited Apr 3 at 6:03
Patrick Roberts
21.3k33677
answered Apr 3 at 5:37
CertainPerformanceCertainPerformance
98.4k166089
1
Not sure if this matters but for multi-unit code points you get the wrong answer, e.g.isUnique('😀😁') === false
– Patrick Roberts
Apr 3 at 5:42
5
The fix is relatively simple though:return new Set(str).size === Array.from(str).length;
– Patrick Roberts
Apr 3 at 5:50
add a comment |
return immediately terminates the function, so only the first iteration if your for loop will ever run. Instead, you should check for whether all characters are unique (if not, return false inside the loop), else return true after the end of the loop:
function isUnique(str) {
let sortedArr = str.split('').sort();
for(let [i,char] of sortedArr.entries()) {
if(char === sortedArr[i + 1]) {
return false
}
}
return true
}
console.log(isUnique('heloworld'))But it would probably be a lot easier to use a Set, and see if its size is equal to the length of the string:
function isUnique(str) {
return new Set(str).size === str.length;
}
console.log(isUnique('heloworld'))
console.log(isUnique('abc'))See comment, thanks Patrick: if you need to account for characters composed of multiple UCS-2 code points (𝟙𝟚𝟛😎😜🙃 etc), call the string iterator and check how many items it returns, which can be done with spread or Array.from (because otherwise, str.length won't evaluate to the right number of individual characters):
function isUnique(str) {
return new Set(str).size === [...str].length;
}
console.log(isUnique('😜'));
console.log(isUnique('😜😜'));edited Apr 3 at 6:03
Patrick Roberts
21.3k33677
answered Apr 3 at 5:37
CertainPerformanceCertainPerformance
98.4k166089
return immediately terminates the function, so only the first iteration if your for loop will ever run. Instead, you should check for whether all characters are unique (if not, return false inside the loop), else return true after the end of the loop:
function isUnique(str) {
let sortedArr = str.split('').sort();
for(let [i,char] of sortedArr.entries()) {
if(char === sortedArr[i + 1]) {
return false
}
}
return true
}
console.log(isUnique('heloworld'))But it would probably be a lot easier to use a Set, and see if its size is equal to the length of the string:
function isUnique(str) {
return new Set(str).size === str.length;
}
console.log(isUnique('heloworld'))
console.log(isUnique('abc'))See comment, thanks Patrick: if you need to account for characters composed of multiple UCS-2 code points (𝟙𝟚𝟛😎😜🙃 etc), call the string iterator and check how many items it returns, which can be done with spread or Array.from (because otherwise, str.length won't evaluate to the right number of individual characters):
function isUnique(str) {
return new Set(str).size === [...str].length;
}
console.log(isUnique('😜'));
console.log(isUnique('😜😜'));function isUnique(str) {
let sortedArr = str.split('').sort();
for(let [i,char] of sortedArr.entries()) {
if(char === sortedArr[i + 1]) {
return false
}
}
return true
}
console.log(isUnique('heloworld'))function isUnique(str) {
let sortedArr = str.split('').sort();
for(let [i,char] of sortedArr.entries()) {
if(char === sortedArr[i + 1]) {
return false
}
}
return true
}
console.log(isUnique('heloworld'))function isUnique(str) {
return new Set(str).size === str.length;
}
console.log(isUnique('heloworld'))
console.log(isUnique('abc'))function isUnique(str) {
return new Set(str).size === str.length;
}
console.log(isUnique('heloworld'))
console.log(isUnique('abc'))function isUnique(str) {
return new Set(str).size === [...str].length;
}
console.log(isUnique('😜'));
console.log(isUnique('😜😜'));function isUnique(str) {
return new Set(str).size === [...str].length;
}
console.log(isUnique('😜'));
console.log(isUnique('😜😜'));edited Apr 3 at 6:03
Patrick Roberts
21.3k33677
answered Apr 3 at 5:37
CertainPerformanceCertainPerformance
98.4k166089
edited Apr 3 at 6:03
Patrick Roberts
21.3k33677
edited Apr 3 at 6:03
Patrick Roberts
21.3k33677
edited Apr 3 at 6:03
Patrick Roberts
21.3k33677
21.3k33677
answered Apr 3 at 5:37
CertainPerformanceCertainPerformance
98.4k166089
answered Apr 3 at 5:37
CertainPerformanceCertainPerformance
98.4k166089
answered Apr 3 at 5:37
CertainPerformanceCertainPerformance
98.4k166089
98.4k166089
1
Not sure if this matters but for multi-unit code points you get the wrong answer, e.g.isUnique('😀😁') === false
– Patrick Roberts
Apr 3 at 5:42
5
The fix is relatively simple though:return new Set(str).size === Array.from(str).length;
– Patrick Roberts
Apr 3 at 5:50
add a comment |
1
Not sure if this matters but for multi-unit code points you get the wrong answer, e.g.isUnique('😀😁') === false
– Patrick Roberts
Apr 3 at 5:42
5
The fix is relatively simple though:return new Set(str).size === Array.from(str).length;
– Patrick Roberts
Apr 3 at 5:50
1
1
Not sure if this matters but for multi-unit code points you get the wrong answer, e.g.
isUnique('😀😁') === false– Patrick Roberts
Apr 3 at 5:42
Not sure if this matters but for multi-unit code points you get the wrong answer, e.g.
isUnique('😀😁') === false– Patrick Roberts
Apr 3 at 5:42
5
5
The fix is relatively simple though:
return new Set(str).size === Array.from(str).length;– Patrick Roberts
Apr 3 at 5:50
The fix is relatively simple though:
return new Set(str).size === Array.from(str).length;– Patrick Roberts
Apr 3 at 5:50
add a comment |
Only first iteration in your for loop is run (because you always execute 'return'). Instead you can use following code
function isUnique(str, t={})
{
return ![...str].some(c=> t[c]=c in t)
}
console.log('heloworld =>',isUnique('heloworld'));
console.log('helo =>',isUnique('helo'));answered Apr 3 at 5:52
Kamil KiełczewskiKamil Kiełczewski
14.1k87397
Why isra parameter?
– JollyJoker
Apr 3 at 8:01
r (I rename it to t) is temporary hash map (define in tricky way as default param)
– Kamil Kiełczewski
Apr 3 at 8:07
add a comment |
Only first iteration in your for loop is run (because you always execute 'return'). Instead you can use following code
function isUnique(str, t={})
{
return ![...str].some(c=> t[c]=c in t)
}
console.log('heloworld =>',isUnique('heloworld'));
console.log('helo =>',isUnique('helo'));answered Apr 3 at 5:52
Kamil KiełczewskiKamil Kiełczewski
14.1k87397
Why isra parameter?
– JollyJoker
Apr 3 at 8:01
r (I rename it to t) is temporary hash map (define in tricky way as default param)
– Kamil Kiełczewski
Apr 3 at 8:07
add a comment |
Only first iteration in your for loop is run (because you always execute 'return'). Instead you can use following code
function isUnique(str, t={})
{
return ![...str].some(c=> t[c]=c in t)
}
console.log('heloworld =>',isUnique('heloworld'));
console.log('helo =>',isUnique('helo'));answered Apr 3 at 5:52
Kamil KiełczewskiKamil Kiełczewski
14.1k87397
Only first iteration in your for loop is run (because you always execute 'return'). Instead you can use following code
function isUnique(str, t={})
{
return ![...str].some(c=> t[c]=c in t)
}
console.log('heloworld =>',isUnique('heloworld'));
console.log('helo =>',isUnique('helo'));function isUnique(str, t={})
{
return ![...str].some(c=> t[c]=c in t)
}
console.log('heloworld =>',isUnique('heloworld'));
console.log('helo =>',isUnique('helo'));function isUnique(str, t={})
{
return ![...str].some(c=> t[c]=c in t)
}
console.log('heloworld =>',isUnique('heloworld'));
console.log('helo =>',isUnique('helo'));answered Apr 3 at 5:52
Kamil KiełczewskiKamil Kiełczewski
14.1k87397
edited Apr 3 at 8:07
answered Apr 3 at 5:52
Kamil KiełczewskiKamil Kiełczewski
14.1k87397
answered Apr 3 at 5:52
Kamil KiełczewskiKamil Kiełczewski
14.1k87397
answered Apr 3 at 5:52
Kamil KiełczewskiKamil Kiełczewski
14.1k87397
14.1k87397
Why isra parameter?
– JollyJoker
Apr 3 at 8:01
r (I rename it to t) is temporary hash map (define in tricky way as default param)
– Kamil Kiełczewski
Apr 3 at 8:07
add a comment |
Why isra parameter?
– JollyJoker
Apr 3 at 8:01
r (I rename it to t) is temporary hash map (define in tricky way as default param)
– Kamil Kiełczewski
Apr 3 at 8:07
Why is
r a parameter?– JollyJoker
Apr 3 at 8:01
Why is
r a parameter?– JollyJoker
Apr 3 at 8:01
r (I rename it to t) is temporary hash map (define in tricky way as default param)
– Kamil Kiełczewski
Apr 3 at 8:07
r (I rename it to t) is temporary hash map (define in tricky way as default param)
– Kamil Kiełczewski
Apr 3 at 8:07
add a comment |
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FWIW:
function noDuplicatedChars() { const chars = new Set(); for (let c of str) { if (chars.has(c)) return false; chars.add(c);} return true; }is a faster alternative.– Frax
Apr 3 at 5:55