Update 279. Perfect Squares.md

TBXark · web-flow · commit abad3756ee57 · 2020-07-31T09:39:37.000+08:00
diff --git a/279. Perfect Squares.md b/279. Perfect Squares.md
@@ -49,20 +49,17 @@ class Solution {
         }
     }
     
-    func isPerfectSquare(n: Int) -> Bool {
-        let sqN = Int(sqrt(Double(n)))
-        return sqN * sqN == n
-    }
-    
     func numSquares(_ n: Int) -> Int {
         guard n > 0 else {
             return 0
         }
         for i in 1...n {
-            if isPerfectSquare(n: i) {
-                perfectSquare.append(i)
-                cache[i] = 1
+            let sq = i * i
+            guard sq <= n else {
+                break
             }
+            cache[sq] = 1
+            perfectSquare.append(sq)
         }
         for i in 1...n {
             if findSum(count: i, num: n) {

Original file line number	Diff line number	Diff line change
`@@ -49,20 +49,17 @@ class Solution {`
`49`	`49`	`}`
`50`	`50`	`}`
`51`	`51`
`52`		`- func isPerfectSquare(n: Int) -> Bool {`
`53`		`- let sqN = Int(sqrt(Double(n)))`
`54`		`- return sqN * sqN == n`
`55`		`- }`
`56`		`-`
`57`	`52`	`func numSquares(_ n: Int) -> Int {`
`58`	`53`	`guard n > 0 else {`
`59`	`54`	`return 0`
`60`	`55`	`}`
`61`	`56`	`for i in 1...n {`
`62`		`- if isPerfectSquare(n: i) {`
`63`		`- perfectSquare.append(i)`
`64`		`- cache[i] = 1`
	`57`	`+ let sq = i * i`
	`58`	`+ guard sq <= n else {`
	`59`	`+ break`
`65`	`60`	`}`
	`61`	`+ cache[sq] = 1`
	`62`	`+ perfectSquare.append(sq)`
`66`	`63`	`}`
`67`	`64`	`for i in 1...n {`
`68`	`65`	`if findSum(count: i, num: n) {`