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leetcode/leetcode/offerII_076.java

+
+
+public class offerII_076 {//剑指 Offer II 076. 数组中的第 k 大的数字
+    public static void main(String[] args) {
+        int[] nums= {3,2,3,1,2,4,5,5,6};
+        int k = 4;
+        System.out.println(Solution076.findKthLargest(nums, k));
+    }
+
+
+
+/*    @Test
+    public static void testling() {
+        int[] a = {2, 3, 1, 5, 3, 4};
+        for (int i = 0; i < 6; i++) {
+            int k = i; //把目前要比的下标记录下
+            for (int j = i; j < 6; j++) {
+                if (a[k] > a[j]) {
+                    int temp = a[k];
+                    a[k] = a[j];
+                    a[j] = temp;
+                }
+            }
+        }
+        for (int i = 0; i < a.length; i++) {
+            System.out.print(a[i]+" ");
+        }
+    }*/
+}
+
+//*********快速排序思想****************************
+class Solution076 {
+    public static int findKthLargest(int[] nums, int k) {
+        int key=0;
+        int left=0;
+        int right= nums.length - 1;
+        quicksort1(nums,key,left,right,k-1);
+
+        return nums[k-1];
+    }
+
+    private static void quicksort1(int[] nums, int key, int left, int right, int k) {
+        if(left>right)
+            return;
+        key = partsort( nums,  key,  left,  right);
+        if(key<k){
+            quicksort1(nums,key+1,key+1,right,k);
+
+        }else if(key==k){
+            return;
+        }else{
+            quicksort1(nums,left,left,key-1,k);
+        }
+    }
+
+    private static int partsort(int[] nums, int key, int left, int right) {
+        int slow=key+1;
+        int fast=key+1;
+
+        int temp;
+        while (fast<=right){
+
+            if(nums[fast]>=nums[key]){
+                temp=nums[slow];
+                nums[slow]=nums[fast];
+                nums[fast]=temp;
+                slow++;
+            }
+            fast++;
+        }
+        slow--;
+        temp=nums[key];
+        nums[key]=nums[slow];
+        nums[slow]=temp;
+        return slow;
+    }
+}
+
+
+//***********先排序************************************
+
+/*
+class Solution076 {
+    public static int findKthLargest(int[] nums, int k) {
+        //排序
+       // bobosort(nums);
+        //快速排序
+        fastsort(nums);
+
+
+        return nums[k-1];
+    }
+
+    private static void fastsort(int[] nums) {
+        int left=0,right= nums.length-1;
+        myquicksort(nums,left,right);
+
+    }
+    private static void myquicksort(int[] nums, int left, int right) {
+        if(left>right)
+            return;
+        int key=partsort(nums,left,right);
+        myquicksort(nums,left,key-1);
+        myquicksort(nums, key+1, right);
+    }
+    private static int partsort(int[] nums, int left, int right) {
+        int key=left;
+        while(left<right){
+            while(left<right&&nums[right]<=nums[key])
+                right--;
+            while(left<right&&nums[left]>=nums[key])
+                left++;
+            myswap(nums,left,right);
+        }
+        myswap(nums,key,left);
+        return left;
+    }
+    private static void myswap(int[] nums, int left, int right) {
+        int tem;
+        tem=nums[left];
+        nums[left]=nums[right];
+        nums[right]=tem;
+    }
+
+
+    public static int[] bobosort(int[] nums){
+        int tem;
+        for (int i = 0; i < nums.length-1; i++) {
+            for (int j = i+1; j < nums.length; j++) {
+                if(nums[i]<nums[j]){
+                    tem=nums[i];
+                    nums[i]=nums[j];
+                    nums[j]=tem;
+                }
+            }
+        }
+
+        return nums;
+    }
+
+}
+*/
+
+//**********k数组存*****************************************
+/*
+
+class Solution076 {
+    public static int findKthLargest(int[] nums, int k) {
+        int[] numk = new int[k];
+        int j=0;
+        for (int i = 0; i < nums.length; i++) {
+            if(i<k){
+                numk[i]=nums[i];
+            }else{
+                j=findKless(numk);
+                if(numk[j]<nums[i])
+                    numk[j]=nums[i];
+            }
+        }
+        j=findKless(numk);
+
+        return numk[j];
+    }
+
+    public static int findKless(int[] nums){
+        int k=0;
+        for (int i = 1; i < nums.length; i++) {
+            if(nums[k]>nums[i])
+                k=i;
+        }
+        return k;
+    }
+}*/
+
+/*
+// new
+class Solution076 {
+    public static int findKthLargest(int[] nums, int k) {
+        int[] numk = new int[k];
+        int j=0;
+        int tag=1;
+        for (int i = 0; i < nums.length; i++) {
+            if(i<k){
+                numk[i]=nums[i];
+            }else{
+                if(tag==1){
+                    j=findKless(numk);
+                    tag=0;
+                }
+                if(numk[j]<nums[i]){
+                    numk[j]=nums[i];
+                    tag=1;
+                }
+            }
+        }
+        j=findKless(numk);
+
+        return numk[j];
+    }
+
+    public static int findKless(int[] nums){
+        int k=0;
+        for (int i = 1; i < nums.length; i++) {
+            if(nums[k]>nums[i])
+                k=i;
+        }
+        return k;
+    }
+}*/