Just push whatever you want to be at -1 to 0, pushing the rest of values further? And start your loop from 1 (so you get x = 0, y = 1). Like this:
double percentMax[5] = {0.0, 0.25, 0.40, 0.80, 1.50};
for(int i = 1; i < 5; i++) {
uniform_random(parcentMax[i-1], percentMax[i]);
}