week one

Author: zhengyingying

Zhengyingying/src/com/zyy/week1/RemoveDuplicates.java

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+package com.zyy.week1;
+
+public class RemoveDuplicates {
+
+	//大神级别
+	public int removeDuplicatesUp(int[] nums) {
+		int i = 0;
+		for (int target : nums) {
+			if (i < 2 || nums[i - 2] < target) {
+				nums[i++] = target;
+			}
+		}
+		for (int k = 0; k < i; k++) {
+			System.out.println(nums[k]);
+		}
+		return i;
+	}
+
+	//菜鸟级别
+	public int removeDuplicates(int[] nums) {
+		int record = 0;
+		int len = nums.length;
+		int[] target = new int[len];
+		int flag = nums[0];
+		target[record++] = flag;
+		int duplicate = 1;
+		for (int i = 1; i < nums.length; i++) {
+			if (nums[i] == flag) {
+				duplicate++;
+				if (duplicate > 2) {
+					len--;
+				} else {
+					target[record++] = flag;
+				}
+			} else {
+				flag = nums[i];
+				if (duplicate != 1) {
+					duplicate = 1;
+				}
+				target[record++] = flag;
+			}
+		}
+		for (int i = 0; i < len; i++) {
+			nums[i] = target[i];
+		}
+		return len;
+	}
+
+	public static void main(String[] args) {
+		int[] nums = { 1, 1, 1, 2, 2, 3, 3, 3 };
+		RemoveDuplicates rd = new RemoveDuplicates();
+		System.out.println(rd.removeDuplicatesUp(nums));
+	}
+}

Zhengyingying/src/com/zyy/week1/SearchInRotatedSortedArray.java

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+package com.zyy.week1;
+
+public class SearchInRotatedSortedArray {
+	public int search1(int[] nums, int target) {
+		int len = nums.length;
+		for (int k = 0; k < len; k++) {
+			if (target == nums[k])
+				return k;
+			else {
+				if (k != len - 1) {
+					if (target > nums[k] && nums[k] > nums[k + 1]) {
+						return -1;
+					}
+				}
+			}
+		}
+		return -1;
+	}
+
+	public static void main(String[] args) {
+		SearchInRotatedSortedArray sisa = new SearchInRotatedSortedArray();
+		int[] nums = { 3, 4, 5, 6, 0, 1 };
+		System.out.println(sisa.search1(nums, 1));
+	}
+}

Zhengyingying/src/com/zyy/week1/SearchInRotatedSortedArrayII.java

@@ -0,0 +1,27 @@
+package com.zyy.week1;
+
+public class SearchInRotatedSortedArrayII {
+
+	public boolean search1(int[] nums, int target) {
+		int len = nums.length;
+		for (int k = 0; k < len; k++) {
+			if (target == nums[k])
+				return true;
+			else {
+				if (k != len - 1) {
+					if (target > nums[k] && nums[k] > nums[k + 1]) {
+						return false;
+					}
+				}
+			}
+		}
+		return false;
+	}
+
+	public static void main(String[] args) {
+		SearchInRotatedSortedArrayII si = new SearchInRotatedSortedArrayII();
+		int[] nums = { 3, 3, 4, 4, 5, 6, 0, 1 };
+		System.out.println(si.search1(nums, 5));
+	}
+
+}

Zhengyingying/src/com/zyy/week1/ThreeSumClosest.java

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+package com.zyy.week1;
+
+import java.util.Arrays;
+
+public class ThreeSumClosest {
+
+	public int binarySearchClosest(int[] num, int target, int start, int end){
+        if(end == start + 1){
+            if(target - num[start] >= num[end] - target) return end;
+            else return start;
+        }
+        else if(end <= start) return start;
+        int mid = (start + end)/2;
+        if(num[mid] == target) return mid;
+        else if(num[mid] < target)  return binarySearchClosest(num, target, mid, end);
+        else return binarySearchClosest(num, target, start, mid);
+    }
+
+    public int threeSumClosest(int[] num, int target) {
+        Arrays.sort(num);
+        int start = 0, end = num.length - 1;
+        int sumValue = 0;
+        int offset = Integer.MAX_VALUE;
+        while(start < end - 1){
+            int item = target - num[start]- num[end];
+            int idx = binarySearchClosest(num, item, start + 1, end - 1);
+            if(idx == start) idx = start+1;
+            else if(idx == end) idx = end -1;
+            if(num[start] + num[end] + num[idx] != target){
+                int oldOfset = offset;
+                offset = Math.min(offset, Math.abs(target - num[start] - num[end] - num[idx]));
+                if(offset != oldOfset){
+                    sumValue = num[start] + num[idx] + num[end];
+                }
+            }
+            if(num[start] + num[end] + num[idx] > target) end--;
+            else if(num[start] + num[end] + num[idx] < target) start++;
+            else {sumValue = target;break;}
+        }
+        return sumValue;
+    }
+
+	public static void main(String[] args) {
+		int[] nums = { -1, 2, 1, -4 };
+		ThreeSumClosest tsc = new ThreeSumClosest();
+		System.out.println(tsc.threeSumClosest(nums, 1));
+	}
+
+}

Zhengyingying/src/com/zyy/week1/TrappingRainWater.java

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+package com.zyy.week1;
+
+public class TrappingRainWater {
+	// 左右两边同时检测，如果右边比左边高，则左边比当前高度低的可以加上差值；
+	// 如果左边比右边高，则右边比当前高度低的可以加上差值。
+	public int trap(int[] height) {
+		int trap = 0;
+		int level = 0;
+		int left = 0, right = height.length - 1;
+		while (left < right) {
+			if (height[left] < height[right]) {
+				level = Math.max(height[left], level);
+				trap += level - height[left];
+				left++;
+			} else {
+				level = Math.max(height[right], level);
+				trap += level - height[right];
+				right--;
+			}
+		}
+		return trap;
+
+	}
+
+	public static void main(String[] args) {
+		int[] height = { 0, 1, 0, 2, 1, 0, 1, 3, 2, 1, 2, 1 };
+		TrappingRainWater trw = new TrappingRainWater();
+		System.out.println(trw.trap(height));
+	}
+
+}

Zhengyingying/src/com/zyy/week1/WordSearch.java

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+package com.zyy.week1;
+
+public class WordSearch {
+
+	public boolean isExist(char[][] board, char[] words, int y, int x, int i) {
+		if (i == words.length)
+			return true;
+		if (y < 0 || x < 0 || y == board.length || x == board[y].length)
+			return false;
+		if ((board[y][x] != words[i]))
+			return false;
+		board[y][x] ^= 256;
+		boolean exist = isExist(board, words, y, x + 1, i + 1)
+				|| isExist(board, words, y + 1, x, i + 1)
+				|| isExist(board, words, y, x - 1, i + 1)
+				|| isExist(board, words, y - 1, x, i + 1);
+		board[y][x] ^= 256;
+		return exist;
+
+	}
+
+	// 回溯
+	public boolean exist(char[][] board, String word) {
+		// 存放word单个字母
+		char[] words = word.toCharArray();
+		for (int i = 0; i < board.length; i++) {
+			for (int j = 0; j < board[i].length; j++) {
+				if (isExist(board, words, i, j, 0))
+					return true;
+			}
+		}
+		return false;
+	}
+
+	public static void main(String[] args) {
+		char[][] board = { { 'A', 'B', 'C', 'E' }, { 'S', 'F', 'C', 'S' },
+				{ 'A', 'D', 'E', 'E' } };
+		WordSearch ws = new WordSearch();
+		System.out.println(ws.exist(board, "ABGGGG"));
+
+	}
+}