add: leetcode 0519 solution

leetcode/0519.Random-Flip-Matrix/519.Random Flip Matrix.go

@@ -0,0 +1,43 @@
+package leetcode
+
+import (
+	"math/rand"
+)
+
+type Solution struct {
+	r     int
+	c     int
+	total int
+	mp    map[int]int
+}
+
+func Constructor(m int, n int) Solution {
+	return Solution{
+		r:     m,
+		c:     n,
+		total: m * n,
+		mp:    map[int]int{},
+	}
+}
+
+func (this *Solution) Flip() []int {
+	k := rand.Intn(this.total)
+	val := k
+	if v, ok := this.mp[k]; ok {
+		val = v
+	}
+	if _, ok := this.mp[this.total-1]; ok {
+		this.mp[k] = this.mp[this.total-1]
+	} else {
+		this.mp[k] = this.total - 1
+	}
+	delete(this.mp, this.total-1)
+	this.total--
+	newR, newC := val/this.c, val%this.c
+	return []int{newR, newC}
+}
+
+func (this *Solution) Reset() {
+	this.total = this.r * this.c
+	this.mp = map[int]int{}
+}