modify code on class

Author: 左程云

src/topinterviewquestions/Problem_0026_RemoveDuplicatesFromSortedArray.java

@@ -9,13 +9,13 @@ public static int removeDuplicates(int[] nums) {
 		if (nums.length < 2) {
 			return nums.length;
 		}
-		int index = 0;
-		for (int i = 0; i < nums.length; i++) {
-			if (i == 0 || nums[i - 1] != nums[i]) {
-				nums[index++] = nums[i];
+		int done = 0;
+		for (int i = 1; i < nums.length; i++) {
+			if (nums[i] != nums[done]) {
+				nums[++done] = nums[i];
 			}
 		}
-		return index;
+		return done + 1;
 	}
 
 }

src/topinterviewquestions/Problem_0029_DivideTwoIntegers.java

@@ -53,14 +53,31 @@ public static int divide(int dividend, int divisor) {
 		if (divisor == Integer.MIN_VALUE) {
 			return dividend == Integer.MIN_VALUE ? 1 : 0;
 		}
+		// 除数不是系统最小
 		if (dividend == Integer.MIN_VALUE) {
 			if (divisor == negNum(1)) {
 				return Integer.MAX_VALUE;
 			}
 			int res = div(add(dividend, 1), divisor);
 			return add(res, div(minus(dividend, multi(res, divisor)), divisor));
 		}
+		// dividend不是系统最小，divisor也不是系统最小
 		return div(dividend, divisor);
 	}
+	// div(a,b) a和b都不能是系统最小
+
+	// 现场福利函数
+	public static String printNumBinary(int num) {
+		StringBuilder builder = new StringBuilder();
+		for (int i = 31; i >= 0; i--) {
+			builder.append(((num >> i) & 1) == 0 ? '0' : '1');
+		}
+		return builder.toString();
+	}
+
+	public static void main(String[] args) {
+		int num = -1;
+		System.out.println(printNumBinary(num));
+	}
 
 }

src/topinterviewquestions/Problem_0033_SearchInRotatedSortedArray.java

@@ -3,49 +3,53 @@
 public class Problem_0033_SearchInRotatedSortedArray {
 
 	public static int search(int[] arr, int num) {
-		int low = 0;
-		int high = arr.length - 1;
-		int mid = 0;
-		while (low <= high) {
-			mid = (low + high) / 2;
-			if (arr[mid] == num) {
-				return mid;
+		int L = 0;
+		int R = arr.length - 1;
+		int M = 0;
+		while (L <= R) {
+			M = (L + R) / 2;
+			if (arr[M] == num) {
+				return M;
 			}
-			if (arr[low] == arr[mid] && arr[mid] == arr[high]) {
-				while (low != mid && arr[low] == arr[mid]) {
-					low++;
+			// arr[M] != num
+			if (arr[L] == arr[M] && arr[M] == arr[R]) {
+				while (L != M && arr[L] == arr[M]) {
+					L++;
 				}
-				if (low == mid) {
-					low = mid + 1;
+				// L和M没撞上，[L]!=[M] L,.....M
+				if (L == M) {
+					L = M + 1;
 					continue;
 				}
 			}
-			if (arr[low] != arr[mid]) {
-				if (arr[mid] > arr[low]) {
-					if (num >= arr[low] && num < arr[mid]) {
-						high = mid - 1;
+			// arr[M] != num
+			// [L] [M] [R] 不都一样的情况
+			if (arr[L] != arr[M]) {
+				if (arr[M] > arr[L]) {
+					if (num >= arr[L] && num < arr[M]) {
+						R = M - 1;
 					} else {
-						low = mid + 1;
+						L = M + 1;
 					}
-				} else {
-					if (num > arr[mid] && num <= arr[high]) {
-						low = mid + 1;
+				} else { //  [L]  >  [M]
+					if (num > arr[M] && num <= arr[R]) {
+						L = M + 1;
 					} else {
-						high = mid - 1;
+						R = M - 1;
 					}
 				}
-			} else {
-				if (arr[mid] < arr[high]) {
-					if (num > arr[mid] && num <= arr[high]) {
-						low = mid + 1;
+			} else { // [L] === [M] ->  [M]!=[R]
+				if (arr[M] < arr[R]) {
+					if (num > arr[M] && num <= arr[R]) {
+						L = M + 1;
 					} else {
-						high = mid - 1;
+						R = M - 1;
 					}
 				} else {
-					if (num >= arr[low] && num < arr[mid]) {
-						high = mid - 1;
+					if (num >= arr[L] && num < arr[M]) {
+						R = M - 1;
 					} else {
-						low = mid + 1;
+						L = M + 1;
 					}
 				}
 			}

src/topinterviewquestions/Problem_0037_SudokuSolver.java

@@ -0,0 +1,56 @@
+package topinterviewquestions;
+
+public class Problem_0037_SudokuSolver {
+
+	public static void solveSudoku(char[][] board) {
+		boolean[][] row = new boolean[9][10];
+		boolean[][] col = new boolean[9][10];
+		boolean[][] bucket = new boolean[9][10];
+		initMaps(board, row, col, bucket);
+		process(board, 0, 0, row, col, bucket);
+	}
+
+	public static void initMaps(char[][] board, boolean[][] row, boolean[][] col, boolean[][] bucket) {
+		for (int i = 0; i < 9; i++) {
+			for (int j = 0; j < 9; j++) {
+				int bid = 3 * (i / 3) + (j / 3);
+				if (board[i][j] != '.') {
+					int num = board[i][j] - '0';
+					row[i][num] = true;
+					col[j][num] = true;
+					bucket[bid][num] = true;
+				}
+			}
+		}
+	}
+
+	public static boolean process(char[][] board, int i, int j, boolean[][] row, boolean[][] col, boolean[][] bucket) {
+		if (i == 9) {
+			return true;
+		}
+		int nexti = j != 8 ? i : i + 1;
+		int nextj = j != 8 ? j + 1 : 0;
+		if (board[i][j] != '.') {
+			return process(board, nexti, nextj, row, col, bucket);
+		} else {
+			int bid = 3 * (i / 3) + (j / 3);
+			for (int num = 1; num <= 9; num++) {
+				if ((!row[i][num]) && (!col[j][num]) && (!bucket[bid][num])) {
+					row[i][num] = true;
+					col[j][num] = true;
+					bucket[bid][num] = true;
+					board[i][j] = (char) (num + '0');
+					if (process(board, nexti, nextj, row, col, bucket)) {
+						return true;
+					}
+					row[i][num] = false;
+					col[j][num] = false;
+					bucket[bid][num] = false;
+					board[i][j] = '.';
+				}
+			}
+			return false;
+		}
+	}
+
+}