Files from offline sessions

Author: rafax

11.go

@@ -0,0 +1,71 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+func main() {
+	strArr := "08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08 49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00 81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65 52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91 22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80 24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50 32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70 67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21 24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72 21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95 78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92 16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57 86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58 19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40 04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66 88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69 04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36 20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16 20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54 01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48"
+	var matrix [20][20]int
+	line := strings.Split(strArr, " ")
+	for i := 0; i < 20; i++ {
+		for j := 0; j < 20; j++ {
+			matrix[i][j], _ = strconv.Atoi(line[i*20+j])
+		}
+	}
+	max := 0
+	for i := 0; i < 20; i++ {
+		for j := 0; j < 20; j++ {
+			curr := maxElementSum(matrix[0:], i, j)
+			if curr > max {
+				max = curr
+			}
+		}
+	}
+	fmt.Println(max)
+}
+
+func maxElementSum(arr [][20]int, x, y int) int {
+	sums := []int{}
+	if x <= 16 && y >= 3 {
+		sum := 1
+		for i := 0; i < 4; i++ {
+			sum *= arr[x+i][y-i]
+		}
+		sums = append(sums, sum)
+	}
+	if x <= 16 {
+		sum := 1
+		for i := 0; i < 4; i++ {
+			sum *= arr[x+i][y]
+		}
+		sums = append(sums, sum)
+	}
+	if x <= 16 && y <= 16 {
+		sum := 1
+		for i := 0; i < 4; i++ {
+			sum *= arr[x+i][y+i]
+		}
+		sums = append(sums, sum)
+	}
+	if y <= 16 {
+		sum := 1
+		for i := 0; i < 4; i++ {
+			sum *= arr[x][y+i]
+		}
+		sums = append(sums, sum)
+	}
+	return max(sums)
+}
+
+func max(sums []int) int {
+	max := 0
+	for _, sum := range sums {
+		if sum > max {
+			max = sum
+		}
+	}
+	return max
+}

12.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+func main() {
+	target := 500
+	triangle := 0
+	for nth := 1; ; nth++ {
+		triangle += nth
+		numFactors := numOfDivisors(triangle)
+		if numFactors > target {
+			fmt.Println(triangle)
+			return
+		}
+		if numFactors%100 == 0 {
+			fmt.Println(numFactors)
+		}
+	}
+}
+
+func numOfDivisors(num int) int {
+	bound := int(math.Ceil(math.Sqrt(float64(num)))) + 1
+	factors := make(map[int]bool)
+	cnt := 2
+	for i := 2; i <= bound; i++ {
+		if num%i == 0 && !factors[i] {
+			factors[i] = true
+			cnt++
+		}
+		res := num / i
+		if res > 1 && num%res == 0 && !factors[res] {
+			factors[res] = true
+			cnt++
+		}
+	}
+	return cnt
+}

13.go

@@ -0,0 +1,16 @@
+package main
+
+import "math/big"
+import "fmt"
+
+func main() {
+	b := [...]string{"37107287533902102798797998220837590246510135740250", "46376937677490009712648124896970078050417018260538", "74324986199524741059474233309513058123726617309629", "91942213363574161572522430563301811072406154908250", "23067588207539346171171980310421047513778063246676", "89261670696623633820136378418383684178734361726757", "28112879812849979408065481931592621691275889832738", "44274228917432520321923589422876796487670272189318", "47451445736001306439091167216856844588711603153276", "70386486105843025439939619828917593665686757934951", "62176457141856560629502157223196586755079324193331", "64906352462741904929101432445813822663347944758178", "92575867718337217661963751590579239728245598838407", "58203565325359399008402633568948830189458628227828", "80181199384826282014278194139940567587151170094390", "35398664372827112653829987240784473053190104293586", "86515506006295864861532075273371959191420517255829", "71693888707715466499115593487603532921714970056938", "54370070576826684624621495650076471787294438377604", "53282654108756828443191190634694037855217779295145", "36123272525000296071075082563815656710885258350721", "45876576172410976447339110607218265236877223636045", "17423706905851860660448207621209813287860733969412", "81142660418086830619328460811191061556940512689692", "51934325451728388641918047049293215058642563049483", "62467221648435076201727918039944693004732956340691", "15732444386908125794514089057706229429197107928209", "55037687525678773091862540744969844508330393682126", "18336384825330154686196124348767681297534375946515", "80386287592878490201521685554828717201219257766954", "78182833757993103614740356856449095527097864797581", "16726320100436897842553539920931837441497806860984", "48403098129077791799088218795327364475675590848030", "87086987551392711854517078544161852424320693150332", "59959406895756536782107074926966537676326235447210", "69793950679652694742597709739166693763042633987085", "41052684708299085211399427365734116182760315001271", "65378607361501080857009149939512557028198746004375", "35829035317434717326932123578154982629742552737307", "94953759765105305946966067683156574377167401875275", "88902802571733229619176668713819931811048770190271", "25267680276078003013678680992525463401061632866526", "36270218540497705585629946580636237993140746255962", "24074486908231174977792365466257246923322810917141", "91430288197103288597806669760892938638285025333403", "34413065578016127815921815005561868836468420090470", "23053081172816430487623791969842487255036638784583", "11487696932154902810424020138335124462181441773470", "63783299490636259666498587618221225225512486764533", "67720186971698544312419572409913959008952310058822", "95548255300263520781532296796249481641953868218774", "76085327132285723110424803456124867697064507995236", "37774242535411291684276865538926205024910326572967", "23701913275725675285653248258265463092207058596522", "29798860272258331913126375147341994889534765745501", "18495701454879288984856827726077713721403798879715", "38298203783031473527721580348144513491373226651381", "34829543829199918180278916522431027392251122869539", "40957953066405232632538044100059654939159879593635", "29746152185502371307642255121183693803580388584903", "41698116222072977186158236678424689157993532961922", "62467957194401269043877107275048102390895523597457", "23189706772547915061505504953922979530901129967519", "86188088225875314529584099251203829009407770775672", "11306739708304724483816533873502340845647058077308", "82959174767140363198008187129011875491310547126581", "97623331044818386269515456334926366572897563400500", "42846280183517070527831839425882145521227251250327", "55121603546981200581762165212827652751691296897789", "32238195734329339946437501907836945765883352399886", "75506164965184775180738168837861091527357929701337", "62177842752192623401942399639168044983993173312731", "32924185707147349566916674687634660915035914677504", "99518671430235219628894890102423325116913619626622", "73267460800591547471830798392868535206946944540724", "76841822524674417161514036427982273348055556214818", "97142617910342598647204516893989422179826088076852", "87783646182799346313767754307809363333018982642090", "10848802521674670883215120185883543223812876952786", "71329612474782464538636993009049310363619763878039", "62184073572399794223406235393808339651327408011116", "66627891981488087797941876876144230030984490851411", "60661826293682836764744779239180335110989069790714", "85786944089552990653640447425576083659976645795096", "66024396409905389607120198219976047599490197230297", "64913982680032973156037120041377903785566085089252", "16730939319872750275468906903707539413042652315011", "94809377245048795150954100921645863754710598436791", "78639167021187492431995700641917969777599028300699", "15368713711936614952811305876380278410754449733078", "40789923115535562561142322423255033685442488917353", "44889911501440648020369068063960672322193204149535", "41503128880339536053299340368006977710650566631954", "81234880673210146739058568557934581403627822703280", "82616570773948327592232845941706525094512325230608", "22918802058777319719839450180888072429661980811197", "77158542502016545090413245809786882778948721859617", "72107838435069186155435662884062257473692284509516", "20849603980134001723930671666823555245252804609722", "53503534226472524250874054075591789781264330331690"}
+	sum := new(big.Int)
+	curr := new(big.Int)
+	for _, num := range b {
+		curr.SetString(num, 10)
+		sum.Add(sum, curr)
+	}
+	fmt.Println(sum.String()[0:10])
+
+}

14.go

@@ -0,0 +1,36 @@
+package main
+
+import "fmt"
+
+func main() {
+	limit := 1000000
+	max := 1
+	maxInd := 1
+	clen := make(map[int]int, 2*limit)
+	for i := 1; i < limit; i++ {
+		len := chainLen(i, clen)
+		if len >= max {
+			max = len
+			maxInd = i
+		}
+	}
+	fmt.Println(maxInd)
+}
+
+func chainLen(n int, clen map[int]int) int {
+	if n == 1 {
+		return 1
+	}
+	len, ok := clen[n]
+	if ok {
+		return len
+	}
+	ret := -1
+	if n%2 == 0 {
+		ret = chainLen(n/2, clen) + 1
+	} else {
+		ret = chainLen(3*n+1, clen) + 1
+	}
+	clen[n] = ret
+	return ret
+}