netfishx's matrix

2007-02-25

排序

sun的官方实现：
private static void sort1(int x[], int off, int len) {
// Insertion sort on smallest arrays
if (len < i="off;" for="" int="" j="i;">off && x[j-1]>x[j]; j--)
swap(x, j, j-1);
return;
}

// Choose a partition element, v
int m = off + (len >> 1); // Small arrays, middle element
if (len > 7) {
int l = off;
int n = off + len - 1;
if (len > 40) { // Big arrays, pseudomedian of 9
int s = len/8;
l = med3(x, l, l+s, l+2*s);
m = med3(x, m-s, m, m+s);
n = med3(x, n-2*s, n-s, n);
}
m = med3(x, l, m, n); // Mid-size, med of 3
}
int v = x[m];

// Establish Invariant: v* (v)* v*
int a = off, b = a, c = off + len - 1, d = c;
while(true) {
while (b <= c && x[b] <= v) { if (x[b] == v) swap(x, a++, b); b++; } while (c >= b && x[c] >= v) {
if (x[c] == v)
swap(x, c, d--);
c--;
}
if (b > c)
break;
swap(x, b++, c--);
}

// Swap partition elements back to middle
int s, n = off + len;
s = Math.min(a-off, b-a ); vecswap(x, off, b-s, s);
s = Math.min(d-c, n-d-1); vecswap(x, b, n-s, s);

// Recursively sort non-partition-elements
if ((s = b-a) > 1)
sort1(x, off, s);
if ((s = d-c) > 1)
sort1(x, n-s, s);
}