ACM 10963 The Swallowing Ground

不難，但我犯了很蠢的錯誤
一開始寫的code是發現y1 - y2不同時就馬上break掉
結果因為這樣寫的話不會把資料讀完，所以吃個四個WA，後來才突然發現到= =


#include <stdio.h>

int main(void)
{
    int t, col, y1, y2, rs, last, notOk, first;

    scanf("%d", &t);
    first = 1;
    while (t--) {
        if (!first)
            printf("\n");
        scanf("%d", &col);
        scanf("%d%d", &y1, &y2);
        if (col == 1 && y1 != y2)
            notOk = 1;
        else
            notOk = 0;
        last = y1 - y2;
        while (--col) {
            scanf("%d%d", &y1, &y2);
            rs = y1 - y2;
            if (rs != last)
                notOk = 1;
            last = rs;
        }
        if (notOk)
            printf("no\n");
        else
            printf("yes\n");
        first = 0;
    }

    return 0;
}