NEW DELHI, June 5 : India's economy grew an unexpectedly strong 7.8 per cent year-on-year in the January-March quarter, the government said on Friday, as robust private investment, farm output and construction activity offset the early impact of the Middle East conflict. The print, the second in an updated data series with a revised base year and wider coverage, was well above a forecast of 7.2 per cent growth in a Reuters poll of economists. Compared with the previous three months, however,