add Solution 455 [golang]

Author: lightfish-zhang

solution/0455.Assign Cookies/Solution.go

@@ -0,0 +1,69 @@
+/* 455 分发饼干
+* 解法
+* 每个小朋友只能最多拥有一块饼干，先满足胃口最大的小孩，剩下的就更容易分配
+* 由于题目没有预先给 g、s 进行排序，需要自己实现快速排序，这里利用goroutine并行运算加速
+* 
+* 21/21 cases passed (40 ms)
+* memory usage (6 MB)
+*/ 
+
+func findContentChildren(g []int, s []int) int {
+	done1 := make(chan struct{})
+	done2 := make(chan struct{})
+	go quickSort_go(g, 0, len(g)-1, done1, 4)
+	go quickSort_go(s, 0, len(s)-1, done2, 4)
+	<-done1
+	<-done2
+	i, j, ret := len(g)-1, len(s)-1, 0
+	for i >= 0 && j >= 0 {
+		if g[i] > s[j] {
+			i--
+		} else {
+			ret++
+			i--
+			j--
+		}
+	}
+	return ret
+}
+
+* 快速排序
+func quickSort(a []int, lo, hi int) {
+	if lo >= hi {
+		return
+	}
+	p := partition(a, lo, hi)
+	quickSort(a, lo, p-1)
+	quickSort(a, p+1, hi)
+}
+func partition(a []int, lo, hi int) int {
+	pivot := a[hi]
+	i := lo - 1
+	for j := lo; j < hi; j++ {
+		if a[j] < pivot {
+			i++
+			a[j], a[i] = a[i], a[j]
+		}
+	}
+	a[i+1], a[hi] = a[hi], a[i+1]
+	return i + 1
+}
+func quickSort_go(a []int, lo, hi int, done chan struct{}, depth int) {
+	if lo >= hi {
+		done <- struct{}{}
+		return
+	}
+	depth--
+	p := partition(a, lo, hi)
+	if depth > 0 {
+		childDone := make(chan struct{}, 2)
+		go quickSort_go(a, lo, p-1, childDone, depth)
+		go quickSort_go(a, p+1, hi, childDone, depth)
+		<-childDone
+		<-childDone
+	} else {
+		quickSort(a, lo, p-1)
+		quickSort(a, p+1, hi)
+	}
+	done <- struct{}{}
+}