二分+三分模板
二分:
返回第一个大于val的数 5 1 3 5 6 9 6 >>9 5 1 3 5 7 9 6 >>7 int bsearch(int val){ int l = 0, r = n; int mid = 0; while (l <= r){ mid = (l + r)>>1; if (a[mid] > val){ r = mid - 1; } else{ l = mid + 1; } } return a[l]; } 返回第一个大于等于val的值: int bsearch(int val){ int l = 0, r = n; int mid = 0; int ans = 0; while (l <= r){ mid = (l + r)>>1; if (a[mid] >= val){ r = mid - 1; ans = mid; } else{ l = mid + 1; } } return a[ans]; } 返回第一个小于val的数 int bsearch(int val){ int l = 0, r = n; int mid = 0; while (l <= r){ mid = (l + r)>>1; if (a[mid] >= val){ r = mid - 1; } else{ l = mid + 1; } } return a[r]; } 5 1 3 5 6 9 6 >>5 返回第一个小于等于val的值: int bsearch(int val){ int l = 0, r = n; int mid = 0; int ans = 0; while (l <= r){ mid = (l + r)>>1; if (a[mid] > val){ r = mid - 1; } else{ l = mid + 1; ans = mid; } } return a[ans]; }
三分:
double solve(double l,double r)
{
double mid,midmid;
while(dbcmp(r - l) > 0)
{
mid = (l + r)/2.0;
midmid = (r + mid)/2.0;
if (getR(mid) >= getR(midmid)) r = midmid;
else l = mid;
}
return getR(l);
}
{
double mid,midmid;
while(dbcmp(r - l) > 0)
{
mid = (l + r)/2.0;
midmid = (r + mid)/2.0;
if (getR(mid) >= getR(midmid)) r = midmid;
else l = mid;
}
return getR(l);
}