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Cod sursa(job #946578)
/* O(n * log n) solution to longest strictly increasing subsequence */
#include <iostream>
#include <string.h>
#include <stdio.h>
#define NMAX 100000
#define ARRAY_SIZE(A) sizeof(A)/sizeof(A[0])
#define FILEIN "scmax.in"
#define FILEOUT "scmax.out"
using namespace std;
int A[NMAX];
int tail[NMAX + 1];
int sol[NMAX];
// Binary search to find the ceil of key in array A (note boundaries in the caller)
int CeilIndex(int A[], int l, int r, int key) {
int m;
while (1) {
if ( l >= r )
break;
m = ( l + r ) / 2;
if ( key >= A[m] ) {
l = m + 1;
} else {
r = m - 1;
}
}
return l;
}
int LongestIncreasingSubsequenceLength(int A[], int size) {
// Add boundary case, when array size is one
int len; // always points empty slot
tail[0] = A[0];
sol[0] = A[0];
len = 1;
for ( int i = 1; i < size; i++ ) {
if( A[i] < tail[0] ) {
// new smallest value
tail[0] = A[i];
if (len == 1) {
sol[0] = A[i];
}
}
else if( A[i] > tail[len-1] ) {
// A[i] wants to extend largest subsequence
sol[len] = A[i];
tail[len++] = A[i];
}
else {
// A[i] wants to be current end candidate of an existing subsequence
// It will replace ceil value in tail
int ceil = CeilIndex(tail, 0, len - 1, A[i]);
tail[ceil] = A[i];
if ( ceil == len - 1 ) {
sol[len - 1] = A[i];
}
}
}
return len;
}
void read_file(const char *filename, int &n )
{
FILE *f = fopen(filename, "r");
fscanf(f, "%d", &n);
for ( int i = 0; i < n; i++ ) {
fscanf(f, "%d", &A[i]);
}
fclose(f);
}
void print_res(const char *filename, const int &res)
{
FILE *f = fopen(filename, "w");
fprintf(f, "%d\n", res);
for (int i = 0; i < res; i++) {
fprintf(f, "%d ", sol[i]);
}
fprintf(f, "\n");
fclose(f);
}
int main()
{
int n;
read_file(FILEIN, n);
int res = LongestIncreasingSubsequenceLength(A, n);
print_res(FILEOUT, res);
return 0;
}