88class TwoStacks {
99 constructor ( capacity ) {
1010 this . data = [ ] ;
11- this . capacity = capacity ;
1211 this . top1 = - 1 ;
1312 this . top2 = capacity ;
13+ 14+ this . capacity = capacity ;
15+ this . total = 0 ;
1416 }
1517
1618 push1 ( value ) {
17- if ( this . top1 === - 1 || this . top1 < this . top2 - 1 ) {
19+ if ( this . total >= this . capacity + 1 ) {
20+ throw new Error ( 'Overflow' ) ;
21+ }
22+ if ( this . top1 < this . top2 - 1 ) {
1823 this . top1 += 1 ;
1924 this . data [ this . top1 ] = value ;
20- return ;
25+ this . total += 1 ;
2126 }
22- throw new Error ( 'Overflow' ) ;
2327 }
2428
2529 push2 ( value ) {
26- if ( this . top2 <= this . capacity && this . top2 > this . top1 ) {
27- this . data [ this . top2 ] = value ;
30+ if ( this . total >= this . capacity + 1 ) {
31+ throw new Error ( 'Overflow' ) ;
32+ }
33+ if ( this . top1 < this . top2 - 1 ) {
2834 this . top2 -= 1 ;
29- return ;
35+ this . data [ this . top2 ] = value ;
36+ this . total += 1 ;
3037 }
31- throw new Error ( 'Overflow' ) ;
3238 }
3339
34- pop1 ( ) { }
40+ pop1 ( ) {
41+ if ( this . top1 >= 0 ) {
42+ const item = this . data [ this . top1 ] ;
43+ this . top1 -= 1 ;
44+ return item ;
45+ }
46+ return - 1 ;
47+ }
3548
36- pop2 ( ) { }
49+ pop2 ( ) {
50+ if ( this . top2 < this . capacity ) {
51+ const item = this . data [ this . top2 ] ;
52+ this . top2 += 1 ;
53+ return item ;
54+ }
55+ return - 1 ;
56+ }
3757}
3858
3959module . exports = TwoStacks ;
4060
4161/** Test cases */
4262
43- const s = new TwoStacks ( 3 ) ;
63+ /*
64+ const s = new TwoStacks(4);
4465
4566s.push1('a');
4667console.log(s.data);
@@ -56,3 +77,11 @@ console.log(s.data);
5677
5778s.push2('b3');
5879console.log(s.data);
80+
81+ console.log(s.pop2());
82+ console.log(s.data);
83+
84+ console.log(s.pop1());
85+ console.log(s.data);
86+
87+ */
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