use a coord struct instead of Sprintf

03/main.go

@@ -33,7 +33,7 @@ func makeScanner(test bool) *bufio.Scanner {
 	return bufio.NewScanner(reader)
 }
 
-type schematic map[string]entry
+type schematic map[coord]entry
 
 type entry struct {
 	num  []rune
@@ -45,12 +45,13 @@ type tmp struct {
 	col int
 }
 
-func key(row, col int) string {
+type coord struct {
-	return fmt.Sprintf("%d.%d", row, col)
+	row int
+	col int
 }
 
 func isSymbol(s schematic, row, col int) bool {
-	if c, ok := s[key(row, col)]; ok {
+	if c, ok := s[coord{row, col}]; ok {
 		return c.symb != 0
 	}
 	return false
@@ -76,17 +77,17 @@ func partOne() {
 				}
 			default:
 				if len(i.tmp) != 0 {
-					schematic[key(row, i.col)] = entry{num: i.tmp}
+					schematic[coord{row, i.col}] = entry{num: i.tmp}
 					i.tmp = []rune{}
 				}
 				if c != '.' {
-					schematic[key(row, col)] = entry{symb: c}
+					schematic[coord{row, col}] = entry{symb: c}
 				}
 			}
 		}
 		// check if we have a number still to save but ran out of line
 		if len(i.tmp) != 0 {
-			schematic[key(row, i.col)] = entry{num: i.tmp}
+			schematic[coord{row, i.col}] = entry{num: i.tmp}
 		}
 		row++
 	}
@@ -94,7 +95,7 @@ func partOne() {
 	// now, map back over the schematics and find the parts
 	for row := 0; row <= 139; row++ {
 		for col := 0; col <= 139; col++ {
-			if entry, ok := schematic[key(row, col)]; ok && entry.symb == 0 {
+			if entry, ok := schematic[coord{row, col}]; ok && entry.symb == 0 {
 				part := mustAtoi(entry.num)
 				if isSymbol(schematic, row, col-1) {
 					// look behind
@@ -139,32 +140,32 @@ func partTwo() {
 				}
 			default:
 				if len(i.tmp) != 0 {
-					schematic[key(row, i.col)] = entry{num: i.tmp}
+					schematic[coord{row, i.col}] = entry{num: i.tmp}
 					i.tmp = []rune{}
 				}
 				if c == '*' { // no longer care about other symbols
-					schematic[key(row, col)] = entry{symb: c}
+					schematic[coord{row, col}] = entry{symb: c}
 				}
 			}
 		}
 		// check if we have a number still to save but ran out of line
 		if len(i.tmp) != 0 {
-			schematic[key(row, i.col)] = entry{num: i.tmp}
+			schematic[coord{row, i.col}] = entry{num: i.tmp}
 		}
 		row++
 	}
 
-	gears := map[string]int{}
+	gears := map[coord]int{}
 	sum := 0
 	// map back over the schematics and find the gears.
 	// there are only ever 1 or 2 parts attached to a gear.
 	for row := 0; row <= 139; row++ {
 		for col := 0; col <= 139; col++ {
-			if entry, ok := schematic[key(row, col)]; ok && entry.symb == 0 {
+			if entry, ok := schematic[coord{row, col}]; ok && entry.symb == 0 {
 				offset := len(entry.num)
 				part := mustAtoi(entry.num)
 				if isSymbol(schematic, row, col-1) {
-					k := key(row, col-1)
+					k := coord{row, col - 1}
 					if gears[k] != 0 {
 						sum += gears[k] * part
 					} else {
@@ -172,7 +173,7 @@ func partTwo() {
 					}
 				}
 				if isSymbol(schematic, row, col+offset) {
-					k := key(row, col+offset)
+					k := coord{row, col + offset}
 					if gears[k] != 0 {
 						sum += gears[k] * part
 					} else {
@@ -181,7 +182,7 @@ func partTwo() {
 				}
 				for i := -1; i < offset+1; i++ {
 					if isSymbol(schematic, row-1, col+i) {
-						k := key(row-1, col+i)
+						k := coord{row - 1, col + i}
 						if gears[k] != 0 {
 							sum += gears[k] * part
 						} else {
@@ -189,7 +190,7 @@ func partTwo() {
 						}
 					}
 					if isSymbol(schematic, row+1, col+i) {
-						k := key(row+1, col+i)
+						k := coord{row + 1, col + i}
 						if gears[k] != 0 {
 							sum += gears[k] * part
 						} else {