> // 2533 Longest Ordered Subsequence
> #include <stdio.h>
> #include <stdlib.h>
> 
> int lcs_length(int x[],int y[],int n);
> int cmp (const void *a,const void *b); 
> void copy(int src[],int dest[],int n);
> /*
> void qsort(int a[],int i,int j);
> int findpivot(int a[],int i,int j);
> int partition(int a[],int l,int r,int pivot);
> void swap(int a[],int i,int j);
> */
> int main()
> {
> 	int a[1001],tmp[1001]; // 0 to 10000 
>     int n;	// 1 <= N <= 1000
> 	int i;
>     scanf("%d",&n);	
> 	for (i=0;i<n;i++) {			
> 		scanf("%d",&a[i]);			
> 	}   	    
> 	copy(a,tmp,n);
> 	qsort(tmp,n,sizeof(int),cmp); 
> 	printf("%d\n",lcs_length(a,tmp,n));
> 	return 0;
> }
> 
> int lcs_length(int x[],int y[],int n) {	
> 	int i,j;
> 	int c[n+1][n+1];	
> 	for (i=1;i<=n;i++) 
> 		c[i][0] = 0;
> 	for (j=0;j<=n;j++) 
> 		c[0][j] = 0;
> 	for (i=1;i<=n;i++) {
> 		for (j=1;j<=n;j++) {
> 			if (x[i-1]==y[j-1]) {
> 				c[i][j] = c[i-1][j-1]+1; 				
> 			} else if (c[i-1][j] >= c[i][j-1]) {
> 				c[i][j] = c[i-1][j];				
> 			} else {
> 				c[i][j] = c[i][j-1];				
> 			}
> 		}
> 	}
> 	return c[n][n];
> }
> 
> int cmp (const void *a,const void *b) 
> { 
> 	return *(int *)a - *(int *)b; 
> } 
> 
> void copy(int src[],int dest[],int n)
> {
> 	int i;
> 	for(i=0;i<n;i++) dest[i]=src[i];
> }
排序要保证是升序，所以排完序应该把相同的元素处理掉吧。不然就是1 2 2这样的都得不出正确答案