Add maximal square solution

cmd/maximalsquare/main.go

@@ -0,0 +1,67 @@
+package main
+
+import "fmt"
+
+type testcase struct {
+	input    []string
+	expected int
+}
+
+var testcases = []testcase{
+	{[]string{"10100", "10111", "11111", "10010"}, 4},
+	{[]string{"10111", "10111", "11111", "10010"}, 9},
+	{[]string{"01"}, 1},
+}
+
+func main() {
+	for _, tc := range testcases {
+		in := make([][]byte, len(tc.input))
+		for i, str := range tc.input {
+			in[i] = []byte(str)
+		}
+
+		res := maximalSquare(in)
+		if res != tc.expected {
+			fmt.Printf("FAIL: %v - got %d, expected %d\n", tc.input, res, tc.expected)
+			continue
+		}
+		fmt.Println("PASS")
+	}
+}
+
+func maximalSquare(matrix [][]byte) int {
+	rows := len(matrix)
+	cols := 0
+	if rows > 0 {
+		cols = len(matrix[0])
+	}
+	maxsqlen := 0
+	prev := 0
+	dp := make([]int, cols+1)
+
+	for i := 1; i <= rows; i++ {
+		for j := 1; j <= cols; j++ {
+			if matrix[i-1][j-1] != 0 {
+				tmp := dp[j]
+				if matrix[i-1][j-1] == '1' {
+					dp[j] = min(min(dp[j-1], prev), dp[j]) + 1
+					if dp[j] > maxsqlen {
+						maxsqlen = dp[j]
+					}
+				} else {
+					dp[j] = 0
+				}
+				prev = tmp
+			}
+		}
+	}
+	return maxsqlen * maxsqlen
+
+}
+
+func min(v1, v2 int) int {
+	if v1 < v2 {
+		return v1
+	}
+	return v2
+}