cs_app 2.73 saturating_add

/*
 * File name: q273.c
 * Author: ZhuTing
 * School: PKU Computer Science
 * Time: 2013-09-15
 */

#include <stdio.h>
#include <stdlib.h>

int saturating_add(int x, int y)
{
	int w = (sizeof(int) << 3) - 1;
	int mark1 = ~(x ^ y) >> w;
	int mark2 = ((x + y) ^ y) >> w;
	int mark = mark1 & mark2;
	int pos = x >> w;
	int ans = ((x + y) & (~(mark)))+ (mark & ((((-1) ^ (1 << w)) & ~pos) + ((1 << w) & pos)));
	return ans;
}

int main()
{
	int a = 0, b = 0;
	scanf("%d%d", &a, &b);
	printf("%d\n", saturating_add(a, b));
	return 0;
}