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Commitbd5e354

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committed
water
1 parentf299cda commitbd5e354

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7 files changed

+310
-9
lines changed

7 files changed

+310
-9
lines changed

‎array/Trap.java

Lines changed: 34 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,7 @@
11
packageAlgorithms.array;
22

33
publicclassTrap {
4-
publicinttrap(int[]A) {
4+
publicinttrap1(int[]A) {
55
if (A ==null) {
66
return0;
77
}
@@ -32,4 +32,37 @@ public int trap(int[] A) {
3232

3333
returnmax;
3434
}
35+
36+
publicinttrap(int[]A) {
37+
// 2:37
38+
if (A ==null) {
39+
return0;
40+
}
41+
42+
intlen =A.length;
43+
int[]l =newint[len];
44+
int[]r =newint[len];
45+
46+
for (inti =0;i <len;i++) {
47+
if (i ==0) {
48+
l[i] =A[i];
49+
}else {
50+
l[i] =Math.max(l[i -1],A[i]);
51+
}
52+
}
53+
54+
intwater =0;
55+
for (inti =len -1;i >=0;i--) {
56+
if (i ==len -1) {
57+
r[i] =A[i];
58+
}else {
59+
// but: use Math, not max
60+
r[i] =Math.max(r[i +1],A[i]);
61+
}
62+
63+
water +=Math.min(l[i],r[i]) -A[i];
64+
}
65+
66+
returnwater;
67+
}
3568
}

‎dp/CanJump.java

Lines changed: 24 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -79,4 +79,28 @@ public static boolean canJump(int[] A, int index) {
7979

8080
returnfalse;
8181
}
82+
83+
// greedy.
84+
publicbooleancanJump4(int[]A) {
85+
// 4:42
86+
if (A ==null) {
87+
returnfalse;
88+
}
89+
90+
intlen =A.length;
91+
92+
intright =0;
93+
for (inti =0;i <A.length;i++) {
94+
right =Math.max(right,i +A[i]);
95+
if (right ==len -1) {
96+
returntrue;
97+
}
98+
99+
if (i ==right) {
100+
returnfalse;
101+
}
102+
}
103+
104+
returntrue;
105+
}
82106
}

‎greedy/Jump.java

Lines changed: 45 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@ public static void main(String[] strs) {
66
System.out.println(jump(A));
77
}
88

9-
publicstaticintjump(int[]A) {
9+
publicstaticintjump1(int[]A) {
1010
if (A ==null ||A.length ==0) {
1111
return0;
1212
}
@@ -31,4 +31,48 @@ public static int jump(int[] A) {
3131

3232
returnsum;
3333
}
34+
35+
// solution 2: one pass greedy.
36+
publicstaticintjump(int[]A) {
37+
if (A ==null ||A.length ==0) {
38+
return0;
39+
}
40+
41+
// bug:
42+
/*
43+
Input: [1]
44+
Output: 1
45+
Expected: 0
46+
*/
47+
if (A.length ==1) {
48+
return0;
49+
}
50+
51+
intlen =A.length;
52+
53+
intstart =0;
54+
intend =0;
55+
56+
intsteps =0;
57+
while (end <len -1) {
58+
intmax =0;
59+
steps++;
60+
for (inti =start;i <=end;i++) {
61+
max =Math.max(max,i +A[i]);
62+
63+
if (max >=len -1) {
64+
returnsteps;
65+
}
66+
}
67+
68+
start =end +1;
69+
end =max;
70+
71+
if (start >end) {
72+
break;
73+
}
74+
}
75+
76+
returnInteger.MAX_VALUE;
77+
}
3478
}

‎hash/SolveSudoku.java

Lines changed: 99 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -1,11 +1,32 @@
11
packageAlgorithms.hash;
22

33
publicclassSolveSudoku {
4-
publicvoidsolveSudoku(char[][]board) {
5-
dfs(board,0,0);
4+
publicstaticvoidmain(String[]args) {
5+
char[][]board = {
6+
{'.','.','9','7','4','8','.','.','.'},
7+
{'7','.','.','.','.','.','.','.','.'},
8+
{'.','2','.','1','.','9','.','.','.'},
9+
{'.','.','7','.','.','.','2','4','.'},
10+
{'.','6','4','.','1','.','5','9','.'},
11+
{'.','9','8','.','.','.','3','.','.'},
12+
{'.','.','.','8','.','3','.','2','.'},
13+
{'.','.','.','.','.','.','.','.','6'},
14+
{'.','.','.','2','7','5','9','.','.'},
15+
};
16+
solveSudoku(board);
17+
for(inti=0;i<9;i++){
18+
for(intj=0;j<9;j++){
19+
System.out.print(board[i][j]);
20+
}
21+
System.out.println();
22+
}
23+
}
24+
25+
publicvoidsolveSudoku1(char[][]board) {
26+
dfs1(board,0,0);
627
}
728

8-
publicbooleandfs(char[][]board,intx,inty) {
29+
publicbooleandfs1(char[][]board,intx,inty) {
930
// go to next row.
1031
if (y ==9) {
1132
y =0;
@@ -19,14 +40,14 @@ public boolean dfs(char[][] board, int x, int y) {
1940

2041
// Skip the solved point.
2142
if (board[x][y] !='.') {
22-
returndfs(board,x,y +1);
43+
returndfs1(board,x,y +1);
2344
}
2445

2546
// Go throught all the possibilities.
2647
for (intk =0;k <9;k++) {
2748
board[x][y] = (char)('1' +k);
2849
// SHOULD RETURN HERE IF INVALID.
29-
if (isValid(board,x,y) &&dfs(board,x,y +1)) {
50+
if (isValid1(board,x,y) &&dfs1(board,x,y +1)) {
3051
returntrue;
3152
}
3253
board[x][y] ='.';
@@ -36,7 +57,7 @@ public boolean dfs(char[][] board, int x, int y) {
3657
returnfalse;
3758
}
3859

39-
publicbooleanisValid(char[][]board,intx,inty) {
60+
publicbooleanisValid1(char[][]board,intx,inty) {
4061
// Judge the column.
4162
for (inti =0;i <9;i++) {
4263
if (i !=x &&board[i][y] ==board[x][y]) {
@@ -68,4 +89,76 @@ public boolean isValid(char[][] board, int x, int y) {
6889

6990
returntrue;
7091
}
92+
93+
// solution 2:
94+
publicstaticvoidsolveSudoku(char[][]board) {
95+
// 3:01
96+
if (board ==null ||board.length ==0 ||board[0].length ==0) {
97+
return;
98+
}
99+
100+
dfs(board,0,0);
101+
}
102+
103+
publicstaticbooleandfs(char[][]board,intx,inty) {
104+
// 3:01
105+
// next row.
106+
if (y >=9) {
107+
returndfs(board,x +1,0);
108+
}
109+
110+
if (x >=9) {
111+
returntrue;
112+
}
113+
114+
// skip the number.
115+
if (board[x][y] !='.') {
116+
returndfs(board,x,y +1);
117+
}
118+
119+
// solve the current node.
120+
for (charc ='0';c <='9';c++) {
121+
board[x][y] =c;
122+
if (isValid(board,x,y,c) &&dfs(board,x,y +1)) {
123+
returntrue;
124+
}
125+
board[x][y] ='.';
126+
}
127+
128+
returnfalse;
129+
}
130+
131+
publicstaticbooleanisValid(char[][]board,intx,inty,charc) {
132+
// the current row.
133+
for (inti =0;i <9;i++) {
134+
if (y !=i &&c ==board[x][i]) {
135+
returnfalse;
136+
}
137+
}
138+
139+
// the current col.
140+
for (inti =0;i <9;i++) {
141+
// BUG: should use board[i][y]
142+
if (x !=i &&c ==board[i][y]) {
143+
returnfalse;
144+
}
145+
}
146+
147+
// the current block.
148+
intstartX =x /3 *3;
149+
intstartY =y /3 *3;
150+
for (intk =0;k <9;k++) {
151+
intindexX =startX +k /3;
152+
intindexY =startY +k %3;
153+
if (indexX ==x &&indexY ==y) {
154+
continue;
155+
}
156+
157+
if (board[indexX][indexY] ==c) {
158+
returnfalse;
159+
}
160+
}
161+
162+
returntrue;
163+
}
71164
}

‎permutation/NextPermutation.java

Lines changed: 37 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -52,4 +52,41 @@ public void swap(int[] num, int i, int j) {
5252
num[i] =num[j];
5353
num[j] =tmp;
5454
}
55+
56+
// Solution 2:
57+
publicvoidnextPermutation2(int[]num) {
58+
if (num ==null) {
59+
return;
60+
}
61+
62+
intlen =num.length;
63+
64+
// Find the index which drop.
65+
intdropIndex = -1;
66+
for (inti =len -1;i >=0;i--) {
67+
if (i !=len -1 &&num[i] <num[i +1]) {
68+
dropIndex =i;
69+
break;
70+
}
71+
}
72+
73+
// replace the drop index.
74+
if (dropIndex != -1) {
75+
for (inti =len -1;i >=0;i--) {
76+
if (num[i] >num[dropIndex]) {
77+
swap(num,dropIndex,i);
78+
break;
79+
}
80+
}
81+
}
82+
83+
// reverse the link.
84+
intl =dropIndex +1;
85+
intr =len -1;
86+
while (l <r) {
87+
swap(num,l,r);
88+
l++;
89+
r--;
90+
}
91+
}
5592
}

‎permutation/PermutationSequence.java

Lines changed: 37 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
11
packageAlgorithms.permutation;
22

3+
importjava.util.LinkedList;
4+
35
/*
46
The set [1,2,3,…,n] contains a total of n! unique permutations.
57
@@ -18,7 +20,7 @@ We get the following sequence (ie, for n = 3):
1820
Note: Given n will be between 1 and 9 inclusive.
1921
* */
2022
publicclassPermutationSequence {
21-
publicstaticStringgetPermutation(intn,intk) {
23+
publicstaticStringgetPermutation1(intn,intk) {
2224
if (n ==0) {
2325
return"";
2426
}
@@ -65,5 +67,39 @@ public static String getPermutation(int n, int k) {
6567
publicstaticvoidmain(String[]args) {
6668
System.out.println(getPermutation(3,5));
6769
}
70+
71+
publicstaticStringgetPermutation(intn,intk) {
72+
// 1:17 -> 1:43
73+
LinkedList<Character>digits =newLinkedList<Character>();
74+
75+
// bug 2: should only add n elements.
76+
for (chari ='1';i <='0' +n;i++) {
77+
digits.add(i);
78+
}
79+
80+
// The index start from 0;
81+
k--;
82+
StringBuildersb =newStringBuilder();
83+
84+
intsum =1;
85+
// n!
86+
for (inti =1;i <=n;i++) {
87+
sum *=i;
88+
}
89+
90+
for (inti =n;i >=1;i--) {
91+
sum /=i;
92+
intdigitIndex =k /sum;
93+
k =k %sum;
94+
95+
//Line 25: error: cannot find symbol: method digits(int)
96+
sb.append(digits.get(digitIndex));
97+
98+
// remove the used digit.
99+
digits.remove(digitIndex);
100+
}
101+
102+
returnsb.toString();
103+
}
68104

69105
}

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