leetcode-73

Author: maslke

src/main/java/medium/lc60.java

@@ -0,0 +1,71 @@
+package medium;
+
+import java.util.List;
+import java.util.ArrayList;
+
+class lc60 {
+    public String getPermutation(int n, int k) {
+        List<Integer> numbers = new ArrayList<>();
+        for (int i = 1; i <= n; i++) {
+            numbers.add(Integer.valueOf(i));
+        }
+        return getPermutation(numbers, k);
+    }
+
+    private String getPermutation(List<Integer> numbers, int k) {
+        int size = numbers.size();
+        if (size == 0) {
+            return "";
+        }
+        if (k == 1) {
+            return getString(numbers);
+        }
+        if (k == count(size)) {
+            return getReverseString(numbers);
+        }
+        while (true) {
+            int count = count(size - 1);
+            if (count < k) {
+                int a = k / count;
+                int b = k % count;
+                if (b == 0) {
+                    Integer p = numbers.get(a - 1);
+                    numbers.remove(a - 1);
+                    return String.valueOf(p) + getReverseString(numbers);
+                } else {
+                    Integer p = numbers.get(a);
+                    numbers.remove(a);
+                    return String.valueOf(p) + getPermutation(numbers, b);
+                }       
+            } else {
+                Integer p = numbers.get(0);
+                numbers.remove(0);
+                return String.valueOf(p) + getPermutation(numbers, k);
+            }
+        }
+    } 
+
+    private int count(int n) {
+        int result = 1;
+        for (int i = 1; i <= n; i++) {
+            result *= i;
+        }
+        return result;
+    }
+
+    private String getString(List<Integer> numbers) {
+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i < numbers.size(); i++) {
+            sb.append(numbers.get(i));
+        }
+        return sb.toString();
+    }
+
+    private String getReverseString(List<Integer> numbers) {
+        StringBuilder sb = new StringBuilder();
+        for (int i = numbers.size() - 1; i >= 0; i--) {
+            sb.append(numbers.get(i));
+        }
+        return sb.toString();
+    }
+}

src/main/java/medium/lc73.java

@@ -0,0 +1,64 @@
+package medium;
+
+class lc73 {
+    public void setZeros(int[][] matrix) {
+        int reserveValue = -1024;
+        for (int i = 0; i < matrix.length; i++) {
+            for (int j = 0; j < matrix[i].length; j++) {
+                if (matrix[i][j] != 0 && hasZero(matrix, i, j)) {
+                    matrix[i][j] = reserveValue;
+                }
+            }
+        }
+
+        // 另外一种可行的方式
+        // for (int i = 0; i < matrix.length; i++) {
+        //     for (int j = 0; j < matrix[i].length; j++) {
+        //         if (matrix[i][j] == 0) {
+        //             setZero(matrix, i, j);
+        //         }
+        //     }
+        // }
+
+        for (int i = 0; i < matrix.length; i++) {
+            for (int j = 0; j < matrix[i].length; j++) {
+                if (matrix[i][j] == reserveValue) {
+                    matrix[i][j] = 0;
+                }
+            }
+        }
+
+    
+    }
+
+    // 将matrix中不为0的数字，设置为特征值
+    private void setZero(int[][] matrix, int i, int j) {
+        for (int m = 0; m < matrix[i].length; m++) {
+            if (matrix[i][m] != 0) {
+                matrix[i][m] = -1024;
+            }
+        }
+
+        for (int m = 0; m < matrix.length; m++) {
+            if (matrix[m][j] != 0) {
+                matrix[m][j] = -1024;
+            }
+        }
+    }
+
+    private boolean hasZero(int[][] matrix, int i, int j) {
+        for (int m = 0; m < matrix[i].length; m++) {
+            if (matrix[i][m] == 0) {
+                return true;
+            }
+        }
+
+        for (int m = 0; m < matrix.length; m++) {
+            if (matrix[m][j] == 0) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}