7272
7373## 解法
7474
75- ### 方法一
75+ ### 方法一:双指针 + 模拟
76+ 77+ 我们用两个变量 $a$ 和 $b$ 分别表示 Alice 和 Bob 的水量,初始时 $a = \text{capacityA},ドル $b = \text{capacityB}$。然后用两个指针 $i$ 和 $j$ 分别指向植物数组的头尾,然后模拟 Alice 和 Bob 从两端向中间浇水的过程。
78+ 79+ 当 $i < j$ 时,我们分别判断 Alice 和 Bob 的水量是否足够浇水,如果不够,我们就重新灌满水罐。然后更新 $a$ 和 $b$ 的水量,同时移动指针 $i$ 和 $j$。最后我们还需要判断 $i$ 和 $j$ 是否相等,如果相等,我们还需要判断 $\max(a, b)$ 是否小于植物的水量,如果小于,我们需要再次重新灌满水罐。
80+ 81+ 时间复杂度 $O(n),ドル其中 $n$ 是植物数组的长度。空间复杂度 $O(1)$。
7682
7783<!-- tabs:start -->
7884
7985``` python
8086class Solution :
8187 def minimumRefill (self plants : List[int ], capacityA : int , capacityB : int ) -> int :
82- i, j = 0 , len (plants) - 1
83- ans = 0
8488 a, b = capacityA, capacityB
85- while i <= j:
86- if i == j:
87- if max (capacityA, capacityB) < plants[i]:
88- ans += 1
89- break
90- if capacityA < plants[i]:
91- capacityA = a - plants[i]
89+ ans = 0
90+ i, j = 0 , len (plants) - 1
91+ while i < j:
92+ if a < plants[i]:
9293 ans += 1
93- else :
94- capacityA -= plants[i]
95- if capacityB < plants[j]:
96- capacityB = b - plants[j]
94+ a = capacityA
95+ a -= plants[i]
96+ if b < plants[j]:
9797 ans += 1
98- else :
99- capacityB -= plants[j]
100- i+= 1
101- j -= 1
98+ b = capacityB
99+ b -= plants[j]
100+ i, j = i + 1 , j - 1
101+ ans += i == j and max (a, b) < plants[i]
102102 return ans
103103```
104104
105105``` java
106106class Solution {
107107 public int minimumRefill (int [] plants , int capacityA , int capacityB ) {
108+ int a = capacityA, b = capacityB;
109+ int ans = 0 ;
108110 int i = 0 , j = plants. length - 1 ;
109- int ans = 0 , a = capacityA, b = capacityB;
110- while (i <= j) {
111- if (i == j) {
112- if (Math . max(capacityA, capacityB) < plants[i]) {
113- ++ ans;
114- }
115- break ;
116- }
117- if (capacityA < plants[i]) {
118- capacityA = a - plants[i];
111+ for (; i < j; ++ i, -- j) {
112+ if (a < plants[i]) {
119113 ++ ans;
120- } else {
121- capacityA -= plants[i];
114+ a = capacityA;
122115 }
123- if (capacityB < plants[j]) {
124- capacityB = b - plants[j];
116+ a -= plants[i];
117+ if (b < plants[j]) {
125118 ++ ans;
126- } else {
127- capacityB -= plants[j];
119+ b = capacityB;
128120 }
129- ++ i;
130- -- j;
121+ b -= plants[j];
131122 }
123+ ans += i == j && Math . max(a, b) < plants[i] ? 1 : 0 ;
132124 return ans;
133125 }
134126}
@@ -138,59 +130,104 @@ class Solution {
138130class Solution {
139131public:
140132 int minimumRefill(vector<int >& plants, int capacityA, int capacityB) {
133+ int a = capacityA, b = capacityB;
134+ int ans = 0;
141135 int i = 0, j = plants.size() - 1;
142- int ans = 0, a = capacityA, b = capacityB;
143- while (i <= j) {
144- if (i == j) {
145- if (max(capacityA, capacityB) < plants[ i] ) ++ans;
146- break;
147- }
148- if (capacityA < plants[ i] ) {
149- capacityA = a - plants[ i] ;
136+ for (; i < j; ++i, --j) {
137+ if (a < plants[ i] ) {
150138 ++ans;
151- } else
152- capacityA -= plants[ i] ;
153- 154- if (capacityB < plants[j]) {
155- capacityB = b - plants[j];
139+ a = capacityA;
140+ }
141+ a -= plants[ i] ;
142+ if (b < plants[ j] ) {
156143 ++ans;
157- } else
158- capacityB -= plants[j];
159- ++i;
160- --j;
144+ b = capacityB;
145+ }
146+ b -= plants[ j] ;
161147 }
148+ ans += i == j && max(a, b) < plants[ i] ;
162149 return ans;
163150 }
164151};
165152```
166153
167154```go
168- func minimumRefill (plants []int , capacityA int , capacityB int ) int {
155+ func minimumRefill(plants []int, capacityA int, capacityB int) (ans int) {
156+ a, b := capacityA, capacityB
169157 i, j := 0, len(plants)-1
170- ans , a , b := 0 , capacityA, capacityB
171- for i <= j {
172- if i == j {
173- if max (capacityA, capacityB) < plants[i] {
174- ans++
175- }
176- break
177- }
178- if capacityA < plants[i] {
179- capacityA = a - plants[i]
158+ for ; i < j; i, j = i+1, j-1 {
159+ if a < plants[i] {
180160 ans++
181- } else {
182- capacityA -= plants[i]
161+ a = capacityA
183162 }
184- if capacityB < plants[j] {
185- capacityB = b - plants[j]
163+ a -= plants[i]
164+ if b < plants[j] {
186165 ans++
187- } else {
188- capacityB -= plants[j]
166+ b = capacityB
189167 }
190- i++
191- j--
168+ b -= plants[j]
169+ }
170+ if i == j && max(a, b) < plants[i] {
171+ ans++
192172 }
193- return ans
173+ return
174+ }
175+ ```
176+ 177+ ``` ts
178+ function minimumRefill(plants : number [], capacityA : number , capacityB : number ): number {
179+ let [a, b] = [capacityA , capacityB ];
180+ let ans = 0 ;
181+ let [i, j] = [0 , plants .length - 1 ];
182+ for (; i < j ; ++ i , -- j ) {
183+ if (a < plants [i ]) {
184+ ++ ans ;
185+ a = capacityA ;
186+ }
187+ a -= plants [i ];
188+ if (b < plants [j ]) {
189+ ++ ans ;
190+ b = capacityB ;
191+ }
192+ b -= plants [j ];
193+ }
194+ ans += i === j && Math .max (a , b ) < plants [i ] ? 1 : 0 ;
195+ return ans ;
196+ }
197+ ```
198+ 199+ ``` rust
200+ impl Solution {
201+ pub fn minimum_refill (plants : Vec <i32 >, capacity_a : i32 , capacity_b : i32 ) -> i32 {
202+ let mut a = capacity_a ;
203+ let mut b = capacity_b ;
204+ let mut ans = 0 ;
205+ let mut i = 0 ;
206+ let mut j = plants . len () - 1 ;
207+ 208+ while i < j {
209+ if a < plants [i ] {
210+ ans += 1 ;
211+ a = capacity_a ;
212+ }
213+ a -= plants [i ];
214+ 215+ if b < plants [j ] {
216+ ans += 1 ;
217+ b = capacity_b ;
218+ }
219+ b -= plants [j ];
220+ 221+ i += 1 ;
222+ j -= 1 ;
223+ }
224+ 225+ if i == j && a . max (b ) < plants [i ] {
226+ ans += 1 ;
227+ }
228+ 229+ ans
230+ }
194231}
195232```
196233
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