feat: add climbing the leaderboard solution

implementation/climbing_the_leaderboard.go

@@ -0,0 +1,62 @@
+package implementation
+
+func searchIndex(ranked []int32, player int32, current int) int32 {
+	// is the first one
+	if ranked[0] < player {
+		return -1
+	}
+
+	// is the last one
+	if ranked[len(ranked)-1] > player {
+		return int32(len(ranked) - 1)
+	}
+
+	// binary search
+	mid := len(ranked) / 2
+	for {
+		if ranked[mid] == player {
+			return int32(mid)
+		}
+
+		if ranked[mid] > player && ranked[mid+1] <= player { // found the middle guy
+			return int32(mid)
+		}
+
+		if ranked[mid] < player {
+			mid = mid / 2
+		} else {
+			mid = mid + mid/2
+		}
+	}
+}
+
+func climbingLeaderboard(ranked []int32, players []int32) []int32 {
+	var result []int32
+	positions := make([]int32, len(ranked))
+
+	counter := int32(1)
+	positions[0] = counter
+
+	for i := 1; i < len(ranked); i++ {
+		if ranked[i] == ranked[i-1] {
+			positions[i] = counter
+		} else {
+			counter++
+			positions[i] = counter
+		}
+	}
+
+	for i := 0; i < len(players); i++ {
+		previous := searchIndex(ranked, players[i], len(ranked)/2)
+
+		if previous == -1 {
+			result = append(result, 1)
+		} else if ranked[previous] == players[i] {
+			result = append(result, positions[previous])
+		} else {
+			result = append(result, positions[previous]+1)
+		}
+	}
+
+	return result
+}

implementation/climbing_the_leaderboard_test.go

@@ -0,0 +1,34 @@
+package implementation
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type ClimbingTheLeaderboard struct {
+	ranked []int32
+	player []int32
+	result []int32
+}
+
+func TestClimbingTheLeaderboard(t *testing.T) {
+	tests := []ClimbingTheLeaderboard{
+		{
+			ranked: []int32{100, 100, 50, 40, 40, 20, 10},
+			player: []int32{5, 25, 50, 120},
+			result: []int32{6, 4, 2, 1},
+		},
+		{
+			ranked: []int32{100, 90, 90, 80, 75, 60},
+			player: []int32{50, 65, 77, 90, 102},
+			result: []int32{6, 5, 4, 2, 1},
+		},
+	}
+
+	for _, test := range tests {
+		assert.Equal(t, test.result, climbingLeaderboard(test.ranked, test.player))
+	}
+}
+
+func TestClimbingTheLeaderboardFiles(t *testing.T) {}