1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
| class Solution {
private String maxValue = String.valueOf(Integer.MAX_VALUE);
public List<String> addOperators(String num, int target) {
List<String> result = new ArrayList<>();
List<Integer> nums = new ArrayList<>();
for (int i = 0; i < num.length(); i++) {
String left = num.substring(0, i + 1);
if (!isValid(left)) {
break;
}
Integer leftNum = Integer.parseInt(left, 10);
nums.add(leftNum);
search(result, num, i + 1, nums, new ArrayList<>(), target);
nums.remove(nums.size() - 1);
}
return result;
}
private void search(List<String> result, String num, int start, List<Integer> nums, List<Character> ops, int target) {
if (start == num.length()) {
if (isEqual(nums, ops, target)) {
String item = convert(nums, ops);
result.add(item);
}
return;
}
for (int i = start; i < num.length(); i++) {
String left = num.substring(start, i + 1);
if (!isValid(left)) {
break;
}
Integer leftNum = Integer.parseInt(left, 10);
nums.add(leftNum);
ops.add('+');
search(result, num, i + 1, nums, ops, target);
ops.set(ops.size() - 1, '-');
search(result, num, i + 1, nums, ops, target);
ops.set(ops.size() - 1, '*');
search(result, num, i + 1, nums, ops, target);
nums.remove(nums.size() - 1);
ops.remove(ops.size() - 1);
}
}
private String convert(List<Integer> nums, List<Character> ops) {
StringBuilder sb = new StringBuilder();
sb.append(nums.get(0));
for (int i = 0; i < ops.size(); i++) {
sb.append(ops.get(i)).append(nums.get(i + 1));
}
return sb.toString();
}
private boolean isEqual(List<Integer> nums, List<Character> ops, int target) {
Deque<Integer> numQueue = new LinkedList<>();
Deque<Character> opQueue = new LinkedList<>();
numQueue.addLast(nums.get(0));
int i = 1;
int j = 0;
while (i < nums.size()) {
numQueue.addLast(nums.get(i));
if (ops.get(j) == '*') {
int first = numQueue.pollLast();
int second = numQueue.pollLast();
if (first != 0 && Integer.MAX_VALUE / first < second) {
return false;
}
int temp = first * second;
numQueue.addLast(temp);
} else {
opQueue.addLast(ops.get(j));
}
i++;
j++;
}
while (!opQueue.isEmpty()) {
int first = numQueue.pollFirst();
int second = numQueue.pollFirst();
int temp;
if (opQueue.pollFirst() == '+') {
temp = first + second;
} else {
temp = first - second;
}
numQueue.addFirst(temp);
}
return numQueue.pollFirst() == target;
}
private boolean isValid(String num) {
if (num.length() == 1) {
return true;
}
if (num.charAt(0) == '0') {
return false;
}
return num.length() < maxValue.length() || num.compareTo(maxValue) < 1;
}
}
|